JPS59109769A - Method of operating direct current arc furnace and connectorfor hearth - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a compacted composite in which the hearth bottom is provided with a metal element in electrical contact with the hearth, either directly or through electrically conductive bricks, such as carbon bricks. , that is, it relates to a method of operating a DC arc furnace constructed from bricks. The invention also relates to a hearth connection device for a DC arc furnace implementing the method.

A furnace of this type with a hearth connection device is disclosed in U.S. Pat.
No. 28,314.

The bottom of known direct current arc furnaces consists of an upper wear lining of a known type, with conductive inserts, for example steel plates or rods. In order to obtain good operating economics, it is important that the wear lining does not wear out for as long as possible. Slag often erodes the wear lining and shortens its life.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for solving the aforementioned and other problems occurring in connection with DC arc furnaces. A feature of this method is that when tapping the molten steel after melting the charge and subjecting it to other treatments, a certain amount of molten steel is left behind, which can be used as part of the starting electrode for the next melting operation. The goal is to make it work. By leaving said sump, for example of molten steel, between the charges, the wear of the wear lining is reduced. This eliminates the temperature shock that occurs when the furnace is completely drained of molten steel and then charged with cold scrap or other cold material. Additionally, the pool of molten steel prevents the slag from contacting the furnace bottom, which is beneficial if the slag significantly attacks the lining material in the furnace.

Recently, grooved operation has been applied to AC furnaces in steelmaking factories, where the quality of tapped steel must be uniform from charge to charge. The disadvantage of this method is that it is not possible to repair the hearth if a sump is used for each charge, as described above.

However, conductive hearth bottoms should not be repaired;
Some argue that it is not a big problem even if the bottom of the hearth with the eaves sump cannot be repaired during operation. This means that the method according to the invention has particular advantages with respect to DC arc furnaces, since an electrically conductive layer is coated. That price υ
When the conductive furnace bottom wears out, the wear lining remains with a minimum thickness, for example 100-150 mm. After that, replace the entire furnace bottom with a spare furnace bottom prepared next to the furnace body.

See, eg, US Pat. No. 4,277,638. A further advantage of the method according to the invention is that it does not require the use of special starting electrodes when operating a DC arc furnace with a reservoir.

The invention also relates to a hearth connection device for a DC arc furnace for carrying out the aforementioned method, the connection device having at least one metal plate and in contact with said metal plate.
It preferably consists of a conductive brick layer. A compaction compound comprising metal elements, such as penetrating spikes or bars, made of steel or of another type of metal or alloy, on said brick or in contact with said plate, i.e. A layer of bricks is provided. A feature of the hearth connection device is that it has a reservoir of molten steel from the previous charge, which reservoir is in contact with the layer of composite, ie, bricks.

In a preferred embodiment of the hearth connection device according to the invention, the sump of molten steel covers the entire conductive part of the hearth bottom, preferably even in the tilted position during normal tapping.

The depth of the aforementioned molten steel layer is so deep that it is not exposed to slag even when the furnace is tilted to tap a normal amount of molten steel.

The method and apparatus according to the invention are illustrated in the accompanying drawings.

The furnace body 1 is provided with a conventional cover, i.e. a lining 2 of metallic material.
is provided. The number of electrodes/'cathodes is not 1 but 2.
In the illustrated example, the electrodes may be hollow; or solid, connected to the cathode.

The material of the electrode 3 is usually graphite. The groove 4 is used, for example, for reduction to produce hot metal, and the solid electrode is normally used for molten steel.

The furnace body is provided with a tapping opening 5 and a scraping opening 6. Below the furnace body there is a hearth connection device, which in its initial position consists of a number of metal plates or rods 7 extending through the layer 8 of compacted composite, i.e. bricks. It consists of Said bar or plate 7 is continuous and has a layer 7 of compacted composite material,
8 and a layer of graphite disposed at the interface with a conductive brick 10, for example a carbon brick, supporting said composite layer. As in ~ the plate or rod 7 penetrates into the layer 9 of graphite, and with it,
Therefore conductive carbon bricks also provide good electrical conductivity. Carbon bricks are arranged in a separate layer, terminating in a metal plate 11, for example made of copper or steel, which extends significantly along the hearth bottom. Said plate covers, for example, the entire hearth bottom and is provided with contacts 11, 12 for connection to the positive pole of the DC power supply. Of course, only one contact may be used. The intention of connecting the entire hearth as well as its extensions is to generally prevent tilting of the shear arc 13 due to current flow in significant parts of the hearth bottom and also around the center of the hearth body.

The hearth connecting plate is provided with a device for air cooling 14 or liquid cooling, preferably both, the intention being to keep said plate as cold as possible, i.e. not damaged by heat from the furnace. It is to do so. See US Pat. No. 4,228,314, supra.

The method according to the invention is carried out as follows.

- After melting the charge, and possibly after further treatment, the furnace is drained of molten steel 15 up to a limit 16, at which point a sump 17 of molten steel is created which covers the conductive part 7 of the furnace bottom. Of course, the reservoir may be left smaller, but it should normally be at least as deep as shown. By increasing it as much as possible, the conductive part of the furnace bottom is made to stand out even in the tilted position of normal tapping of P1 molten steel, so that the slag does not come into contact with the conductive part of the furnace bottom,
The wear lining may be prevented from being eroded unnecessarily.

The hearth connection device consists of a well-known layer 11 made of metal, 1 carbon brick
0, and an electrically conductive layer 8, 7 on the top of which said reservoir 17, for example of molten steel or hot metal. Thus, a hearth connection device is provided which is comprised of the various layers described above and the layer 17 of molten metal.

The method and device according to the invention can be varied in various ways within the scope of the claims.

[Brief explanation of drawings]

The drawing is a cross-sectional view of a DC arc furnace. In the figure, 1...furnace body 3...electrode 4...groove 5.
・・Tapping opening 6 ・Road or plate 8 ・Brick layer 9 ・Graphite layer 10 ・Carbon brick 11 ・Plate 1
3... Arc 14... Cooling device 15... Molten steel 16... Limit 17... Reservoir agent Asamura Akira 4 people

Claims (1)

[Claims] (1) The hearth bottom connects to the hearth connection device (11) directly or through a conductive brick (10) such as a carbon brick.
a compacted composite with a metal element in conductive contact with the
That is, in the method of operating a DC arc furnace constructed of bricks, after melting the charge (15) and possibly further treatment, during the tapping of said molten steel, a certain amount of molten steel is left behind, said residual molten steel , i.e. the reservoir (17) acts as part of the starting electrode for the next melting operation, and said reservoir (17)
A method for operating a DC arc furnace, characterized in that the amount of molten steel is such that it completely covers the conductive bottom of the furnace even in a tilted position during normal tapping of molten steel. (2. In the method according to claim 1, the residual reservoir (IT) completely covers the conductive furnace bottom and also adequately covers the tilted position of normal tapping of molten steel. A method of operating a DC arc furnace characterized by: (3) at least one metal plate (11);
a layer of electrically conductive bricks, such as carbon bricks, possibly in contact with said plate (11), said bricks being disposed on top of said bricks or otherwise disposed in contact with said sillage (11); a compacting compound (8), i.e. a layer of bricks, said latter layer of bricks being made of steel, or another type of metal, or an alloy of metal elements (7), such as through-plates or bars; A hearth connection device for a direct current arc furnace comprising: a hearth for a direct current arc furnace, characterized in that it comprises a sump (17)k of molten steel from a previous nayage in contact with the last mentioned layer; Connection device. (4) A device according to claim 6, characterized in that the reservoir covers the entire electrically conductive part of the hearth bottom and preferably also in the tilted position of normal tapping. Hearth connection device for arc furnaces.