JPH04313682A - Method for preventing arc deflection in DC electric furnaces - Google Patents

Abstract

PURPOSE:To protect a furnace wall from damage and inhibit the generation of melting residues of scraps and obtain high productivity by installing a furnace bottom anode electrode in pin structure in such a fashion that it may be deviated to an anti arc deflection side. CONSTITUTION:A furnace anode electrode is designed under a single pin structure several pins structure. The magnetic field produced by a secondary conductor 1 connected with the furnace bottom anode electrode 5 forces an arc 2 to be deviated by the angle theta to a cinder outlet from the opposite side of a transformer 3. As the deflection of this arc 2 melts and damages the refractories of a furnace wall 4, the furnace bottom anode 5 on the lower part is installed in such a fashion that it may be deviated to the direction of an anti-arc deflection. This construction prevents an arc 1 from directly reaching the furnace wall and protects the refractories from melting damage.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a method for preventing arc deflection in a DC electric furnace. More specifically, the present invention relates to a method for preventing arc deflection in a DC electric furnace, which suppresses problems such as damage to furnace wall refractories and unmelted scrap, and allows melting to be performed with high productivity.

0002

[Prior Art] Electric furnaces have been widely used for melting scrap raw materials, etc., and a DC type electric furnace has been developed, and its use in steel melting is being considered. . This DC electric furnace has, for example, the configuration shown in Fig. 1, in which electrodes such as an upper cathode and a lower bottom anode are arranged in a DC furnace with refractories arranged on the furnace wall, and a predetermined current is applied. The system operates according to conditions such as , voltage, etc.

[0003] This DC electric furnace has attracted attention in terms of operational efficiency and productivity, but since the arc during melting is deflected, it has become a serious issue to deal with this problem. . That is, as can be seen for example in FIG. 2, during high current operation in a DC electric furnace, arc deflection occurs in accordance with Fleming's left-hand rule due to the influence of the magnetic field generated by the lower secondary conductor. This deflection of the arc becomes larger as the current is increased to increase the melting efficiency. The deflection of this arc causes local melting and damage to the refractories of the furnace lid and furnace wall.

[0004] Since this melting loss and damage requires repair of the refractories of the electric furnace, an increase in production costs and a decrease in production efficiency are unavoidable, which has become a major problem. Such an arc deflection is, for example, approximately 14 N for the arrangement shown in the top view of FIG.
When the force acts and the lower secondary conductor is introduced from the transformer side at an angle α of about 68°, an arc is deflected from the anti-transformer side toward the slag outlet at an angle θ of about 37°, The amount of erosion on the furnace wall due to this deflection is at an angle θ≒20~40°
It was confirmed that it would be extremely large.

In order to suppress problems such as melting damage caused by such arc deflection, measures such as cooling the refractory furnace wall have been considered, but there is no satisfactory solution. This is the reality. This invention was made in view of the above circumstances, and provides a DC electric furnace melting method that improves the shortcomings of conventional DC electric furnaces, suppresses melting and damage to refractories, and has excellent productivity. In particular, the object is to provide a method for preventing arc deflection.

[0006]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention is characterized in that a furnace bottom anode electrode having a single or plural pin structure is arranged unevenly on the anti-arc deflection side. A method for preventing arc deflection in a DC electric furnace is provided. The method of the present invention will be described in detail below. In the method of the present invention, for example, as shown in FIG. 4 corresponding to FIG. 3, the lower secondary conductor (1) (α is The arc (2) is deflected from the side opposite to the transformer (3) side to the slag outlet side in an angular direction of θ = 30 to 40 degrees due to the magnetic field generated by the angle (approximately 68 degrees), so this unavoidable arc In order to prevent the deflection of (1) from eroding the refractories on the furnace wall (4), the lower furnace bottom anode electrode (5) is unevenly located from the center of the furnace bottom (5') to the side opposite to the arc deflection direction. let This prevents the arc (1) from directly reaching the furnace wall (4), thereby preventing melting and damage to the refractory.

In this case, the bottom anode electrode (5) of the electric furnace has a single pin (51) as shown in FIG.
and the Keller type, which consists of a plurality of pins (52) as shown in Figure 6.
) type, but any of these types of electrodes (5
), these electrodes (5) are also moved toward the opposite arc deflection direction.
be unevenly distributed. In this case, in the case of the Keller type electrode shown in FIG. 6, as illustrated in FIG.
By reducing the number of pins (52) or increasing the arrangement density of pins (52) in the direction opposite to the arc deflection direction,
The electrodes (5) can be unevenly distributed as described above.

The direction of arc deflection and the anti-arc deflection direction in which the bottom electrode (5) is arranged are determined by the position of the lower secondary conductor arranged in the electric furnace, as shown in FIG. Therefore, in consideration of the position of the lower secondary conductor, the electric furnace is configured so that the bottom anode electrode (5) is unevenly distributed on the side opposite to the deflection of the arc. Of course, in the method of this invention, water cooling means etc. are employed on the furnace wall etc. on the arc deflection side.
Damage caused by arcs may be suppressed, and in combination with this, obstacles caused by arc deflection may be more effectively removed.

[0009] Also in such a case, the furnace bottom anode electrode (5)
The uneven distribution of can be an extremely effective means. Although the degree of uneven distribution of the electrode (5) varies depending on the size and capacity of the electric furnace, it is preferably about 1.0 to 3.0 times the diameter of the electrode. In the case of a Keller type electrode, the magnitude of the uneven distribution of the assumed centers of the plurality of pins can be set to this level. Of course, this number is not critical.

[0010] Hereinafter, the method of the present invention will be explained in more detail by way of examples.

[0011]

[Example] First, arc melting was carried out using a DC electric furnace having the configuration shown in FIG. 1 and having a conventional single-pin bottom anode electrode. The specifications and operating conditions of the electric furnace in this case were as follows.・Furnace capacity (actual operation) 25t ・Furnace shell diameter 4,000mm ・Upper cathode 14 inches x 1 ・Transformer (actual operation) 15MVA ・Secondary current MA×40KA ・Input power 10MW ・Steel type SUS304 ・Tapping temperature 1550 ℃ ・Average melting amount 23t/ch ・Tap-Tap (%) 95 ・Arc voltage 400V ・Arc current 25KA ・Approximate arc length ~370mm ・Lower secondary conductor introduction angle (α) Approximately 68°As shown in Figure 3 When arc deflection occurred and θ was 30°, the melting loss of the refractory reached a maximum defect thickness of 220 mm, which was extremely large compared to the top thickness of 320 mm.

[0012] Therefore, the anode electrode, which had been placed at the center of the furnace bottom, was unevenly distributed in the direction opposite to the arc deflection direction by about twice its diameter. As a result, erosion of wall refractories due to arc deflection was suppressed. Productivity has improved significantly. Of course, this invention is not limited to the above sides. Various details are possible.

[0013]

[Effects of the Invention] The method of this invention suppresses problems such as damage to refractories such as furnace walls and unmelted scrap.
Melting can be performed with high productivity.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional block diagram illustrating the configuration of a DC electric furnace.

FIG. 2 is a perspective cross-sectional view showing deflection of an arc.

FIG. 3 is a plan view showing the positional relationship between arc deflection and furnace wall damage.

FIG. 4 is a plan view showing uneven distribution of hearth bottom electrodes in the method of this invention.

FIG. 5 is a cross-sectional view showing an ilcid type electrode.

FIG. 6 is a sectional view showing a Keller type electrode.

FIG. 7 is a plan view illustrating uneven distribution in the case of a Keller type electrode.

[Explanation of symbols]

1 Lower secondary conductor 2 Arc 3 Transformer 4 Furnace wall 5 Hearth bottom anode electrode 51 Single pin 52 Multiple pins

Claims (1)

[Claims] 1. A method for preventing arc deflection in a DC electric furnace, characterized in that a furnace bottom anode composed of one or more pin structures is arranged unevenly on the side opposite to arc deflection.