JPH02213692A - Dc arc furnace - Google Patents

Abstract

PURPOSE:To solve the shortage of heat of a projection body and to prevent melt remainder of metal scrap by providing auxiliary electrodes suspended on a steel outlet at the body. CONSTITUTION:A bottom electrode 4 is buried in the central bottom of a furnace shell 1, and rodlike auxiliary electrodes 10, 10 suspended on a steel outlet 5 are provided at a projection body 2. A furnace cover 9 is removed, metal scrap is charged in the shell 1, the electrode 4 is connected to the positive electrode of a DC power source, a rodlike electrode 8 is connected to the negative electrode, and energized. In this case, when a DC or AC power source is also connected between the electrodes 10 and 10, even if the electrode 4 is not conducted with metal scrap, melting can be started, and melted steel melted by the electrodes 10, 10 is fed on the electrode 4 soon. Accordingly, the scrap can be efficiency melted by a direct arc between the electrodes 4 and 8. If an arc is so generated in the degree as to supplement type heat radiation of the body 2 between the electrodes 4 and 4, melt remainder of the scrap is not formed on the body 2, and the temperature of the melted steel can be made uniform.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a DC arc furnace for melting metal scrap and the like.

[Conventional technology]

As is well known, arc furnaces that melt metal scraps and the like using high heat generated by an arc are classified into alternating current and direct current types depending on the power source used. AC type has been used more widely than DC type because the power supply equipment is relatively simple, but AC type generates induced current in the surrounding area, has large power transmission loss due to skin effect, and has electrode wear. It is disadvantageous compared to the DC type in terms of speed, etc., and the DC type only requires one rod-shaped electrode, and by using the rod-shaped electrode as the negative electrode and the bottom electrode as the positive electrode, the melt can be efficiently arced. Recently, research has been conducted into more efficient use of DC arc furnaces, as they have advantages such as heating ability.

On the other hand, an arc furnace known from Japanese Patent Application Laid-Open No. 59-86887 has, for example, a projecting body part integrally formed by projecting a part of the furnace shell constituting the furnace body outward; A tap hole that can be opened and closed is formed on the bottom wall of the body, and is tiltably supported so that the tap hole can be lowered during tapping, and the tilting angle of the furnace body required for tapping is small. This method has advantages such as improved quality because it is difficult for slag to be caught in the tapped metal.

[Problems with conventional technology]

However, when the tiltable arc furnace described in the above-mentioned conventional Japanese Patent Application Laid-Open No. 59-86887 is provided with a furnace bottom electrode and a DC power source is used therefor, although it has the above-mentioned advantages, it has the following problems. occurred. That is, since heat easily escapes from the protruding body to the outside, it is difficult to melt the metal scrap in the protruding body, and melting tends to leave a residue, and the temperature of molten steel is low in the protruding body and the temperature distribution is not uniform. The quality is uneven.

Additionally, when trying to start melting after introducing scrap, if there is a gap between the scraps at the bottom of the furnace and the scrap is not electrically connected to the bottom electrode, there is a problem that an arc cannot be generated and melting cannot start. .

Means for Solving Problem c] The present invention aims to solve the above problems and provide a DC arc furnace in which the temperature distribution of molten steel is improved (melting is always easy). A DC arc in which a part of the furnace shell constituting the main body is made to protrude outward to integrally form a protruding body part on one side, and a tapping port that can be freely opened and closed is formed on the bottom wall of the protruding body part. The furnace is characterized in that the protrusion is provided with an auxiliary electrode that hangs down over the tap.

〔Example〕

Next, one embodiment of the present invention will be described with reference to the drawings.

In the figure, a furnace shell 1 constituting a furnace body is formed of a refractory material into a circular container shape in plan view, and a projecting body part 2 is integrally formed on one side by projecting a part of the shell outward. The bottom wall 3 is formed in the shape of a gentle mortar bottom extending from the bottom of the furnace shell 1 to the bottom of the projecting body 2. A furnace bottom electrode 4 is buried in the bottom of the center of the furnace shell 1, and a tapping port 5 is provided at the bottom of the protrusion 2. Reference numeral 6 denotes a closing plate pivotally attached to the lower surface of the bottom wall 3 by a bin 7, and the closing plate 6 is kept in close contact with the opening end surface of the tapping port 5 as shown in the figure except when tapping the tap. is obstructed. , 8 is a rod-shaped electrode that extends through the furnace lid 9 and hangs down from the center of the furnace shell 1 so as to face the furnace bottom electrode 4. Accordingly, in the present invention, a rod-shaped auxiliary electrode 10.10 is provided on the protruding body portion 2 so as to hang down above the tap hole 5. The entire furnace shell l is supported by furnace legs (not shown) whose lower edges are formed in an arc shape so that it can be tilted, and the tapping port 5 is moved from the upright state shown in the figure by the operation of a cylinder or motor.
can be tilted so that it is lowered.

In the DC arc furnace configured in this way, the furnace cover 9 is removed, metal scrap is put into the furnace shell 1, and the furnace bottom electrode 4 is connected to the positive pole of the DC power supply, and the rod-shaped electrode 8 is connected to the negative pole to energize. . At that time, if a DC or AC power source is also connected between the auxiliary electrodes 10 and 10 and an arc is generated between the auxiliary electrodes 10 and 10, melting will occur even if the bottom electrode 4 is not electrically connected to the metal scrap. Since the molten steel melted at the auxiliary electrode 10.10 eventually flows onto the bottom electrode 4, the metal scrap can be efficiently melted by the DC arc between the bottom electrode 4 and the rod-shaped electrode 8. If an arc is generated between the auxiliary electrodes 10 and 10 to compensate for the heat dissipation of the protruding body part 2, there will be no unmelted metal scrap on the protruding body part 2, and the temperature of the molten steel can be made uniform. . When tapping, the molten steel at the bottom of the furnace can be extracted by tilting the tapping port 5 downward and removing the closing plate 6. Even at this time, if an arc is generated at the auxiliary electrodes 10 and 10, the temperature of the molten steel in the vicinity of the tapping port 5 can be maintained by the heating, and the fluidity of the molten steel can be maintained, so that the steel can be tapped smoothly.

〔Effect of the invention〕

In this way, the present invention uses a bottom-extrusion method that allows high-quality molten steel to be obtained in a DC arc furnace with excellent thermal efficiency, and solves the lack of heat in the protruding body part by providing an auxiliary electrode. The melting of metal scrap in the protruding body portion has beneficial effects such as preventing the formation of residues and improving the temperature distribution of molten steel.

[Brief explanation of the drawing]

The drawings show an embodiment of the DC arc furnace according to the present invention, with FIG. 1 being a longitudinal sectional view and FIG. 2 being a plan view thereof. DESCRIPTION OF SYMBOLS 1... Furnace shell, 2... Projection body part, 3... Bottom wall, 4...
... Hearth bottom electrode, 5... Steel tapping port, 8... Rod-shaped electrode, l
O...Auxiliary electrode.

Claims (1)

[Claims] A direct current system in which a part of the furnace shell constituting the furnace body is made to protrude outward to integrally form a protruding body part on one side, and a tapping port that can be opened and closed is formed on the bottom wall of the protruding body part. A DC arc furnace characterized in that an auxiliary electrode is provided on the protruding body portion and hangs down above the tapping port.