Bottom electrode structure of electric arc furnace

Details Bottom electrode structure of electric arc furnace Bottom electrode structure of electric arc furnace

1999-11-29

2003-10-21

Hoang, Tu Ba (Department: 3742)

Industrial electric heating furnaces

Arc furnace device

Furnace body detail

C373S094000, C373S052000

Reexamination Certificate

active

06636548

ABSTRACT:

FIELD OF THE INVENTION
The present invention generally relates to a direct current (DC) electrical arc furnace, and in particular to a bottom electrode of a DC electrical arc furnace.
BACKGROUND OF THE INVENTION
Electrical arc furnaces have been widely used in refining metals, especially steel. Generally speaking, an electrical arc furnace takes the advantage of opposite electrodes arranged on top and bottom of a vessel to generate electrical arcs for melting raw material of metal disposed in the vessel. An example of the electrical arc furnace is disclosed in U.S. Pat. No. 5,191,592 issued on Mar. 2, 1993 to Robert A. Janiak and Nicolas Meysson and assigned to Clecim.
FIG. 1
of the attached drawings shows the general structure of an electrical arc furnace. The electric arc furnace comprises a vessel
10
, a top electrode
12
arranged on the top of the vessel
10
and several bottom electrodes
14
fixed to and extending through a bottom lid
16
of the vessel
10
. The electrodes
12
,
14
are connected to a power source, such as an electric main, for generating electric arc therebetween to melt the raw materials of metal disposed in the vessel
10
.
FIG. 9
shows conventional bottom electrodes
14
mounted to the bottom lid
16
of the vessel
10
. The bottom lid
16
defines a plurality of through holes
20
in which the bottom electrodes
14
are received. Each bottom electrode
14
has mounting means
22
for being mounted to the bottom lid
16
by bolts
24
. The bottom lid
16
is attached to a bottom opening
28
of the vessel
10
by means of fastening pins
26
whereby the bottom electrodes
14
are partially inserted into the vessel
10
.
Referring to
FIGS. 10-12
, each bottom electrode
14
comprises an elongate electrode body
30
. The mounting means
22
comprises a circumferential flange
32
extending from a lower portion of the electrode body
30
. A ring connection member
34
is positioned on the circumferential flange
32
and fixed thereto by bolts
36
. The ring connection member
34
has an inside diameter substantially greater than an outside diameter of the electrode body
30
thereby defining a ring space
38
therebetween. The ring connection member
34
defines a plurality of holes
40
for receiving the bolts
24
that secure the ring connection member
34
to the bottom lid
16
. The ring connection member
34
has an outside diameter greater than an inside diameter of the corresponding hole
20
of the bottom lid
16
for completely closing the hole
20
.
A first insulation ring
42
is interposed between the bottom lid
16
of the vessel
10
and the ring connection member
34
and a second insulation ring
44
is interposed between the ring connection member
34
and the circumferential flange
32
of the bottom electrode
14
for electrically isolating the bottom electrode
14
from the vessel
10
. An insulation collar
46
is fixed to the inside diameter of the ring connection member
34
.
On the bottom lid
16
of the vessel
10
, refractory material
48
in powder form are disposed as shown in
FIGS. 12 and 13
for protection of the vessel
10
. During the refining process, heavy metal impurity, such as lead, is molten and penetrates through the refractory powders
48
and sinks toward the bottom lid
16
as shown by curved lines of FIG.
13
. Drainage holes
49
are defined in the bottom lid
16
through which the impurity flows out of the vessel
10
. Conventionally, the impurity that flows out of the vessel
10
through the drainage holes
49
is not properly guided and may get contact with the bottom electrodes
14
. Since the molten metal inside the vessel
10
and the bottom electrodes
14
are in general not in the same electrical potential, the contact therebetween causes a short-circuiting resulting in damage to the furnace thereby reducing the service life thereof and increasing the overall costs. The electric arc furnace disclosed in Clecim patent has to be inspected after 1500 batches and the bottom electrodes
14
have to changed. This causes an increase of costs.
Thus, it is desired to provide a bottom electrode of electric arc furnace in order to overcome the problems discussed above.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a bottom electrode of an electric arc furnace comprising impurity guide means for properly guiding the impurity flowing out of the furnace without contacting the bottom electrode thereby eliminating short-circuiting problem and reducing the costs.
Another object of the present invention is to provide a bottom electrode of an electric arc furnace, which has an extended service life thereby reducing the overall costs.
To achieve the above object, in accordance with the present invention, there is provided a bottom electrode of a direct current electric arc furnace comprising an electrode body extending through a hole defined in a bottom of the furnace. A circumferential flange is formed around a lower portion of the electrode body to which a ring connection member is attached. The connection member forms a ring channel defined by inner and outer walls from which inner and outer flanges radially extend in opposite directions. The inner flange is fixed to the circumferential flange of the electrode body by bolts. The outer flange is fixed to the furnace bottom for attaching the bottom electrode to the furnace bottom. The channel is located between the circumferential flange of the electrode body and an inside diameter of the hole defined in the furnace bottom for increasing radial distance between the electrode body and the hole of the furnace bottom. Insulative members are arranged on and under the circumferential flange of the electrode body for electrically isolating the electrode from the furnace bottom.


REFERENCES:
patent: 5191592 (1993-03-01), Janiak et al.
patent: 5268924 (1993-12-01), Sakakibara et al.
patent: 5835523 (1998-11-01), Becker et al.

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