Plastic and nonmetallic article shaping or treating: processes – Furnace lining formation or repair
Patent
1994-12-23
1997-07-08
Aftergut, Karen
Plastic and nonmetallic article shaping or treating: processes
Furnace lining formation or repair
264 36, 266281, 427140, 501112, B32B 3500, C04B 3504, C21B 706, F27D 116
Patent
active
056457723
DESCRIPTION:
BRIEF SUMMARY
The present invention pertains to the use of a refractory ceramic mass for lining the bottoms of d.c. furnaces (direct-current electric furnaces), especially d.c. arc furnaces. One or more electrodes, which cooperate with one or more electrodes extending downward from the cover of the furnace to a point located a short distance in front of the area of the metal bath, are arranged in these furnaces. The present invention also pertains to a process for repairing the bottom linings of such furnaces.
Two types of d.c. electric arc furnaces have basically been known. In both cases, an electrode, usually the cathode, which may also be a multipart electrode, is arranged in the area of the furnace cover, and it extends to a point shortly in front of the metal bath.
In contrast, the lining of the counterelectrode (anode) differs. In one case, the bottom of the furnace is prepared completely with an electrically conductive, refractory ceramic lining, and thus it joins the metallic bottom electrode of the furnace, which is connected as the anode.
In the other case, the lining of the furnace bottom consists of conventional refractory bricks and masses, into which one or more separate electrodes extend.
The present invention pertains to the latter embodiment of DC furnaces.
It is obvious that it is very difficult to compact especially the area between the electrodes (anodes) in the bottom area of the furnace in the case of [ceramic] body linings. Consequently, wear will be more rapid precisely in this area than in adjacent sections of the bottom lining. Depending on the type and the extent of the erosion, the electrodes, which are normally covered by the refractory ceramic lining, will be exposed as well.
Repairing the refractory lining ([ceramic] mass) in this area is especially difficult because there is a risk of destruction or insulation of the electrodes. The complete lining (including the electrodes) has therefore hitherto been replaced, especially when the electrodes themselves have already been (partially) attacked (worn). This is difficult, and it costs a lot of money and time.
The present invention will remedy this situation and show a possibility of how the service life of bottom linings of d.c. furnaces can be prolonged.
The present invention is based on the consideration that the function of the electrode and consequently the durability of the bottom lining can be maintained or prolonged in a surprisingly simple manner by using a ceramic mass which makes electrical conductivity possible and thus ensures an electrically conductive contact with the metallic bottom electrodes, which are equally subject to wear, instead of a conventional, electrically nonconductive, refractory lining.
Even such ceramic masses have been known, in principle, for electric furnaces of the above-mentioned first design, in which the entire bottom is used as a counterelectrode, the prior-art ceramic linings do contain carbon, which is undesirable in many fields of application.
In contrast, the present invention proposes a refractory ceramic lining or repair mass, which is to be used in the area of the electrodes, and which contains 10 to 40 wt. % of finely dispersed metallic additives, besides one or more refractory ceramic oxides. These metallic additives preferably consist of iron.
The finely dispersed iron powder, which is homogeneously distributed in the refractory ceramic matrix, melts at ca. 1,400.degree. C., and forms very fine channels, which are uniformly interspersed in the refractory ceramic matrix material, as a result of which sufficient electrical conductivity is also guaranteed in this area. Thus, the electrically conductive refractory ceramic mass also assumes a (partial) function of the bottom electrodes, which may have partially been already destroyed.
Even though ceramic a body consisting of refractory oxides and metal particles has been known from DATABASE WPI, Week 8348, Derwent Publications Ltd., AN 83-829648, it is used for molds for vacuum casting. The refractory oxides are said to be more finely dispersed tha
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Eckstein Wilfried
Petio Franz-Adolf
A. Earley III John F.
Aftergut Karen
Early John F. A.
Veitsch-Radex Aktiengesellschaft fur Feuerfeste Erzeugnisse
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