JP2985346B2 - Hearth structure of DC arc furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hearth structure in a DC arc furnace, and more particularly to a structure in which a refractory brick is constructed around a bottom electrode.

[0002]

2. Description of the Related Art In general, a DC arc furnace has electrodes provided on the bottom of a vessel-shaped furnace body, and electrode rods are inserted and arranged from above the furnace body, and the electrode is placed between the electrode rods and the furnace bottom electrode. It is widely known as a melting furnace for melting scrap steel and the like by the heat of a generated DC arc.

[0003] The furnace bottom electrode in such a DC arc furnace generally has a large heat load such as Joule heat generated by a current flowing through the electrode, and in addition to a molten metal such as molten steel heated to a high temperature. There is a problem that wear is remarkable because of the contact, and the bottom of the furnace body surrounding such an electrode is usually formed of a stamp material made of a refractory powder such as magnesia. However, there is also an inherent problem that the refractory made of such powders is greatly worn due to contact with the molten metal in the furnace during operation of the furnace, thereby further adversely affecting the furnace bottom electrode. I was

[0004]

In order to reduce the wear of the hearth surface and the wear of the hearth electrode when using a DC arc furnace, the present inventors have made various studies and found that the bottom part of the furnace body, particularly the furnace, In the area surrounding the bottom electrode, a refractory brick made of a material with little erosion, for example, magnesia-carbonaceous brick, is arranged, thereby effectively avoiding erosion of the furnace bottom and, consequently, adverse effects on the furnace bottom electrode. I found something to gain. As a result of further studies by the present inventors, when the hearth surface is formed by using such refractory bricks, in order to prevent floating based on expansion due to heat, fireproof It has been found that it is necessary to form a trapezoidal shape on a predetermined surface of the brick to form a curved concave hearth.

[0005]

Here, the present invention has been completed based on such knowledge, and the gist of the present invention is that a furnace is provided at a substantially central portion of a mildly curved concave hearth surface of a furnace body. In a hearth structure in a DC arc furnace in which a bottom electrode is provided and an arc discharge between the furnace bottom electrode and an electrode rod hanging down from above is used to melt a molten material such as scrap steel, Around the furnace bottom electrode, a block-shaped refractory brick is arranged concentrically around the furnace bottom electrode, and the refractory brick is formed into a trapezoidal shape whose four sides gradually become narrower toward the furnace upper side. Give
In addition, the furnace floor is formed by providing a trapezoidal shape whose upper surface and lower surface gradually narrow in width toward the furnace center side.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, in order to clarify the present invention more specifically, typical embodiments of the present invention will be described in detail with reference to the drawings. It should not be construed as limiting in any way by the description of the examples,
It should be understood that various changes, modifications, improvements and the like can be made based on the knowledge of those skilled in the art without departing from the scope of the present invention.

First, FIGS. 1 and 2 show an example of a DC arc furnace having a hearth structure according to the present invention. There, the arc furnace is provided with a side wall 2 made of a known refractory.
A furnace body having a bottom wall 4 and a known bottom electrode device 8 having a columnar electrode body 6 embedded in the center of the bottom wall 4 of the furnace body. It has a structure. Although not shown in the figure, an electrode rod is arranged to be suspended from above in the furnace, as is well known, and a direct current is applied between the electrode rod and the electrode body 6. An arc is generated, and the heat causes the iron raw material such as scrap steel to melt.

The electrode body 6 constituting the furnace bottom electrode device 8 may be any known electrode made of a metal such as iron, and may be an electrode made of a plurality of pins in addition to a rod. Even so, there is no problem.

At the bottom of the furnace body of such a DC arc furnace, a block-shaped refractory brick 10 located on the bottom wall 4 is arranged concentrically around the electrode body 6 around the electrode body 6. While being arranged in a plurality of rows, between the bricks 10 and the furnace bottom electrode device 8, and between the bottom wall 4,
A well-known powdered refractory 12 such as magnesia carbon is filled and compacted to form a mildly curved concave, substantially flush furnace bottom 14.

That is, the refractory brick 10 is shown in FIG.
As is clear from FIG. 4 and FIG. 4, the upper surface (A) and the lower surface (B) are directed toward the center of the furnace, and the four side surfaces (C, D, E, F) are: Each has a trapezoidal shape in which the width gradually decreases toward the upper part of the furnace. Thus, by using such a brick 10 and arranging the furnace bottom in a predetermined number of rows in the circumferential direction around the electrode body 6 (electrode device 8) and further in the radial direction, the shape of the bottom wall 4 is obtained. Correspondingly, a mildly curved concave hearth surface 14 is formed.

As the refractory brick 10, any brick made of a known refractory can be used, but in particular, because of its good wear resistance, an unfired brick made of magnesia carbon is used. Is preferably adopted. Also,
It is desirable that the size and shape of the brick 10 be appropriately selected depending on the arc furnace to be applied, the location of the brick in the hearth, and the like.

By the way, in a DC arc furnace having a hearth structure having such a structure, when melting scrap steel or the like, a molten material is filled in a container-shaped furnace body according to a conventional method, and the furnace body opening is opened. An electrode, such as a graphite electrode, is hung from above the electrode, and while the opening is covered, an electric current is applied between the electrode and the furnace bottom electrode 6, and the heat generated by the DC arc generated thereby causes the melting. It dissolves the material.

Further, in the present invention, even in such a melting operation, since the hearth is constituted by the bricks 10 having the above-described structure, compared with the case of using a powdered refractory as in the prior art, Wear can be advantageously reduced and uplift of the brick can be well avoided by the specific brick shape.

Incidentally, according to the results of the experiments conducted by the present inventors, a concave hearth surface is formed by using the refractory brick according to the present invention in place of the conventional stamp material, whereby the hearth surface is reduced. The erosion rate is reduced from an average of 1.5 mm / charge of the powdered refractory to 0.5 mm / charge, significantly improving the wear resistance and thereby reducing the effect on the hearth electrode and the electrode itself. The average wear rate was from 3.5 mm / charge to 0.9 mm / charge, and the wear of the electrodes could be significantly reduced.

[0015]

As is apparent from the above description, in the hearth structure of the DC arc furnace according to the present invention, the hearth electrode located at the center of the hearth is centered and concentrically formed therearound. In addition, the block-shaped refractory bricks, each of which has a trapezoidal shape gradually narrowing in width, with four side faces facing the furnace upper side and upper and lower faces facing the furnace center side, are arranged. From what it is, when operating the furnace,
The wear of the refractory bricks due to contact with the molten metal, and thus the increase in the wear of the furnace bottom electrode due to the wear of the bricks, can be advantageously reduced, and the lifting of the bricks can also be effectively avoided. As a result, the durability of the DC arc furnace was improved.

[Brief description of the drawings]

FIG. 1 is an explanatory sectional view showing one embodiment of a hearth structure of a DC arc furnace according to the present invention.

FIG. 2 is a half cutaway plan view of the hearth structure in FIG.

FIG. 3 is an explanatory plan view of a refractory brick used in the hearth structure in FIG. 1;

FIG. 4 is an explanatory front view of a refractory brick used in the hearth structure in FIG. 1;

[Explanation of symbols]

 6 Electrode body 8 Furnace bottom electrode device 10 Refractory brick 12 Powder refractory 14 Hearth surface

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F27B 3/08 F27B 3/14 F27D 1/04

Claims (1)

(57) [Claims] An arc between the furnace bottom electrode and an electrode rod suspended from above in a furnace body, wherein a furnace bottom electrode is provided at a substantially central portion of a mildly curved concave hearth surface of the furnace body. By electric discharge, a hearth structure in a DC arc furnace in which a melting material such as scrap steel material is melted, and around the hearth electrode, a block-shaped refractory brick is arranged concentrically around the hearth electrode, The refractory brick is
The furnace floor surface having a trapezoidal shape in which two side surfaces gradually decrease in width toward the furnace upper side, and an upper surface and a lower surface thereof provide a trapezoidal shape in which the width gradually decreases toward the furnace center side; A hearth structure in a DC arc furnace, characterized by forming: