JP2001012855A - Bottom electrode of dc electric furnace and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent local heating due to a current concentration, to prolong an electrode using period and to facilitate a maintenance by installing a solid electrode made of a composite material obtained by filling a magnesia refractory material as an aggregate with an iron-based alloy as a matrix at a bottom of a DC electric furnace. SOLUTION: An anode is made of an iron-base alloy 10 as a matrix and obtained by filling an MgO aggregate 11 as a refractory material. In this case, since an area occupying the alloy is relatively large, its self-heating due to an electrode concentration is prevented, thereby preventing local fusing. Since the alloy 10 is eroded as number of times of charging is increased but a steel of a residue of molten steel compensates it, its lifetime can be prolonged. In the case of a conventional magnesia carbon electrode, a molten steel component is retained on a surface of a furnace bottom so as to disturb an adherence of the magnesia carbon, but by such a this electrode structure, an eroded portion is supplemented by the dissolved iron component retained at the bottom.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bottom electrode of a DC electric furnace.

[0002]

2. Description of the Related Art Conventionally, as a bottom electrode of a DC electric furnace, an air-cooled multi-pin type in which an electrode composed of a plurality of steel contact pins is air-cooled, and a water-cooled type in which an electrode composed of a single thick steel rod is water-cooled. Type billet molds have been used. These types of bottom electrodes are excellent in that steel has good conductivity and generates less heat, but even when cooled, the steel melts away due to the molten metal, so the life is short, and the frequency of hearth repairs increases. I will. As a countermeasure, a conductive brick electrode in which magnesia carbon, which can extend the life by one digit or more compared to a steel electrode, is widely spread on a copper plate at the furnace bottom is used.

[0003]

However, since the magnesia carbon electrode has lower conductivity than steel, it must be spread over a large area in order to suppress the resistance, and when a large current is applied, the current is concentrated. Therefore, there is a problem that a hot spot is formed and magnesia carbon is easily melted locally.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has as its object to prevent local heating due to current concentration, prolong the electrode use period, and facilitate maintenance.

[0005]

According to the present invention, an iron-based alloy is used as a matrix, and a magnesia (MgO) or the like is used in order to secure current conduction so that current concentration hardly occurs and to provide erosion resistance to molten steel. Characterized in that a solid electrode made of a composite filled with the refractory material as an aggregate is mounted on the furnace bottom. Further, a method of manufacturing a furnace bottom electrode according to the present invention is characterized in that a powder composite of an iron-based alloy and a refractory material is pressed and then forged to form a solid electrode. Further, the method for manufacturing a furnace bottom electrode according to the present invention is characterized in that a composite mixture of an iron-based alloy and a refractory material is melted, cast and rapidly cooled to obtain a solid electrode. Further, the method of manufacturing a furnace bottom electrode according to the present invention is characterized in that a powder of an iron-based alloy and a refractory material is pressed and then sintered to form a solid electrode. Further, the method for manufacturing a furnace bottom electrode according to the present invention is characterized in that an amorphous mixture of an iron-based alloy and a refractory material is directly applied to the furnace bottom and solidified by self-sintering.

[0006]

Embodiments of the present invention will be described below. FIG. 1 is a view for explaining a DC electric furnace using the bottom electrode of the present invention, and FIG. 2 is a sectional view of the bottom electrode.
A DC electric furnace 1 is provided with a carbon (graphite) cathode 2 at the upper part, an anode 3 composed of a matrix of an iron-based alloy and filled with magnesia-based aggregate at the furnace bottom, and a stamp around the anode. Lumber 4 is laid. Cathode 2 and anode 3
Between 200 and 300, for example,
A voltage of V is applied, and a large current of, for example, about 100 KA flows through the scrap 6 placed in the furnace to generate heat and melt the scrap.

As shown in FIG. 2, the anode 3 is made of an iron-based alloy 10
Is a matrix and is filled with MgO aggregate as a refractory material.Since the area occupied by the iron-based alloy is relatively large, self-heating due to current concentration can be prevented, and local fusing can be prevented. . Of course, as the number of charges increases, the iron-based alloy 10 melts down, but the steel in the rest of the melt compensates for this,
The service life can be extended. In the case of a conventional magnesia carbon electrode, the melted portion is repaired with a hot repair material consisting of MgO and tar-pitch, but the molten steel component remains on the furnace bottom surface and this Although it has hindered the adhesion, the electrode structure of the present invention has an advantage that the molten iron component remaining at the furnace bottom compensates for the eroded portion.

The following is an example of a method for manufacturing a furnace bottom electrode. Forging method For example, iron powder, magnesia powder, and carbon are mixed in a volume ratio of 4:
4: Mix at a ratio of about 2, press once, forge and densify. Arc melting method A complex mixture of iron or its alloy and magnesia is melted in an arc, cast and quenched. Sintering method Iron or its alloy and magnesia are powdered, mixed, pressed, and then heat-treated to obtain a sintered body. Powder stamping method Laminate the furnace bottom with an amorphous (powder) mixture in the same manner as the stamp material, and remove gas to make it denser. Thereafter, self-sintering is performed by heating with a molten metal. In this case, tar, pitch and the like may be added in order to impart fluidity and shape retention to the mixture.

The material mixed as the aggregate of the furnace bottom electrode is not limited to magnesia, but may be a general refractory material such as zirconia, alumina, calcium oxide, and zircon.

FIG. 3 is a diagram showing an example of a furnace bottom electrode according to the present invention. This example shows a case without carbon,
And MgO aggregate 11 are mixed.
It is.

[0011]

As described above, according to the present invention, a solid electrode made of a composite in which an iron-based alloy is used as a matrix and a refractory material is used as an aggregate is mounted on the furnace bottom, so that current concentration is prevented. As a result, local overheating is prevented, and the electrode usage period can be extended. In addition, since the rest of the molten metal forms a repair layer, the stability is increased, and there is no need for special cooling, thereby facilitating maintenance.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a DC electric furnace in which a furnace bottom electrode of the present invention is used.

FIG. 2 is a sectional view of a furnace bottom electrode.

FIG. 3 is a diagram showing an example of a furnace bottom electrode of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electric furnace 1, 2 ... Carbon cathode, 3 ... Anode, 4 ... Stamp material, 5 ... DC power supply, 6 ... Scrap, 10 ... Iron-base alloy, 11 ... MgO, 12 ... Pores.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3K084 AA00 AA01 CA08 CA09 CA10 CC07 4K045 AA04 BA02 BA10 RB02 RB08 4K063 AA03 AA04 AA12 BA02 BA13 CA05 FA53 FA64 FA73 FA76

Claims (5)

[Claims] 1. A furnace bottom electrode for a DC electric furnace, wherein a solid electrode made of a composite filled with an iron-based alloy as a matrix and a refractory material as an aggregate is mounted on the furnace bottom. 2. A method of manufacturing a bottom electrode of a DC electric furnace, wherein a powder composite of an iron-based alloy and a refractory material is pressed and then forged into a solid electrode. 3. A method for manufacturing a bottom electrode of a DC electric furnace, in which a composite mixture of an iron-based alloy and a refractory material is melted, cast and rapidly cooled to form a solid electrode. 4. A method for manufacturing a bottom electrode of a DC electric furnace, wherein a powder of an iron-based alloy and a refractory material is pressed and then sintered to form a solid electrode. 5. A method for manufacturing a bottom electrode of a DC electric furnace in which an amorphous mixture of an iron-based alloy and a refractory material is directly applied to a furnace bottom to form a solid electrode by self-sintering.