JP2946621B2 - Furnace bottom structure of electric furnace - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a furnace bottom structure in an electric furnace having a furnace bottom electrode, for example, a DC arc furnace or a direct current furnace.

[Conventional technology]

In an electric furnace of this type, a furnace bottom plate and a furnace bottom electrode at the furnace bottom are electrically insulated by an insulator.

[Problems to be solved by the invention]

However, if lead is mixed in the raw material, when the raw material is melted, the molten lead penetrates into the refractory object and cracks from the upper surface of the refractory at the bottom of the furnace, and the lead becomes When it reaches the location, the electrical insulation between the furnace bottom plate and the furnace bottom electrode is broken, causing a spark accident, and making the furnace inoperable. In addition, there is a problem that the life of the furnace bottom electrode is shortened and limited due to such dielectric breakdown.

The present invention has been made in order to solve the above-mentioned problems (technical problems) of the prior art, and when molten lead attempts to penetrate, the molten lead is solidified at a position before reaching the insulator. An object of the present invention is to provide a furnace bottom structure of an electric furnace in which an electric insulation state between a furnace bottom plate and a furnace bottom electrode can be favorably maintained.

[Means for solving the problem]

In order to achieve the above object, the present invention employs the means described in the claims, and the operation is as follows.

[Action]

In the case of melting the molten raw material in the furnace, when the molten lead permeates the refractory from the upper surface of the furnace bottom refractory, the molten lead is cooled by the cooling member and solidifies before reaching the insulator. Therefore, the electrical insulation state between the furnace bottom plate and the furnace bottom electrode is well maintained.

〔Example〕

Hereinafter, drawings showing an embodiment of the present application will be described. Reference numeral 1 denotes a furnace bottom in a DC arc furnace, which is constituted by a furnace bottom plate 2 formed of a metal material, for example, a steel plate and forming an outer shell of the furnace bottom, and a refractory 3 lined on the upper surface thereof. Reference numeral 4 denotes a place where the molten metal formed on the upper side of the furnace bottom 1 is located.
The refractory 3 is composed of a main body 5 and a complementary portion 7 fitted in a through hole 6 formed in the main body 5, and between the inner peripheral surface of the through hole 6 and the outer peripheral surface of the complementary portion 7. Is refractory for filling 8
Is packed.

Next, reference numeral 10 denotes a holding plate for the furnace bottom electrode, which is formed of a strong metal plate, for example, a steel plate. Reference numeral 11 denotes a furnace bottom electrode provided so as to penetrate the furnace bottom plate 2 and the refractory 3 and is formed of, for example, a steel rod, and is integrated with the holding plate 10 by welding. The complementary part 7 is integrated with the holding plate 10 and the furnace bottom electrode 11. A conducting conductor 13 is connected via a connection terminal 12 to a lower end of the furnace bottom electrode 11 protruding outside the furnace. The furnace bottom electrode 11 is attached to the holding plate 10 by using one having a relatively large diameter as shown in the figure. But instead,
A large number of small diameter pins may be used as the furnace bottom electrode 11 and attached to the holding plate 10 respectively. That is, a structure called a KELLER type may be used. Reference numeral 14 denotes an insulating portion interposed between the annular receiving portion 2a of the hearth plate 2 and the peripheral portion of the holding plate 10 for electrically insulating the hearth plate 2 and the hearth electrode 11 from each other. is there.

Next, 15 and 16 are cooling members embedded in the refractory 3 between the upper surface 3a of the refractory 3 and the insulator 14. Of these, the cooling member 15 is buried around the lower part of the edge of the through hole 6 in the main body 5, and the cooling member 16 is buried in the lower part of the outer peripheral portion of the complementary part 7.
Located near. Each of these cooling members 15 and 16 is formed by coiling a pipe body through which a cooling medium can pass. The pipe is made of steel or copper. The pipe body may be provided with fins so as to effectively perform cooling as described later.

In the DC arc furnace, the raw material (for example, scrap) in the storage location 4 is charged, and the raw material is melted by supplying electric power between the upper electrode (not shown) and the furnace bottom electrode 11 as is well known. It becomes molten metal (for example, molten steel) 20.

During the operation of the furnace as described above, heat from the molten metal 20 is transmitted to the furnace bottom 1 and the temperature of the refractory 3 and the furnace bottom plate 2 rises. For this reason, when lead is mixed in the raw material, the lead melted by the above-mentioned melting is applied to the refractory 3 from the upper surface 3a of the refractory 3.
Or the cracks, or between the furnace bottom electrode 11 and the complementary portion 7 of the refractory 3. However, during the above operation, a cooling medium such as cooling water or a cooling gas is flowed through the cooling members 15 and 16 as indicated by arrows 17 and 18, respectively. As a result, the refractory 3 around the cooling members 15, 16 is kept at a temperature lower than the melting point of lead (327 ° C.). Therefore, even if molten lead permeates as described above,
The molten lead solidifies before reaching the insulator 14 and does not enter the area of the solidification line 21 indicated by a two-dot chain line, for example. As a result, the furnace bottom plate 2 and the furnace bottom electrode
The electrical insulation between 11 is well maintained.

When the refractory 3 is newly installed, the temperature of the furnace bottom 1 is about 250 ° C. when the refractory 3 is newly installed. 3
Due to the melting of the lead or an increase in the apparent thermal conductivity due to the permeation of the lead, the temperature becomes higher than the melting point of the lead in a relatively short time. However, as described above, the cooling by the cooling members 15 and 16 prevents the penetration of molten lead into the electrically insulating portion between the furnace bottom plate 2 and the furnace bottom electrode 11 as described above, and maintains the electrical insulation between them. Dripping.

〔The invention's effect〕

As described above, in the present invention, even if molten lead attempts to infiltrate from the upper surface 3a of the refractory 3 toward the insulator 14 during operation of the electric furnace, the molten lead solidifies before reaching the insulator 14. By doing so, the electrical insulation between the furnace bottom plate 2 and the furnace bottom electrode 11 can be maintained, and there is utility in that the operation of the electric furnace can be continued without hindrance.

[Brief description of the drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is a longitudinal sectional view showing a furnace bottom structure of an electric furnace. DESCRIPTION OF SYMBOLS 1 ... Furnace bottom, 2 ... Furnace bottom plate, 3 ... Refractory, 11 ... Furnace bottom electrode, 14 ... Insulator, 15, 16 ... Cooling member.

Claims (1)

(57) [Claims] A furnace bottom comprising a furnace bottom plate and a refractory lined on an upper surface thereof is provided with a furnace bottom electrode penetrating the furnace bottom and the refractory. In a furnace bottom structure of an electric furnace electrically insulated by an insulator between the furnace bottom electrode and the refractory between the insulator on the upper surface of the refractory, the refractory is insulated from the upper surface of the refractory. A bottom structure of an electric furnace, wherein a cooling member for cooling and solidifying lead penetrating toward a body is provided.