Industrial electric heating furnaces – Arc furnace device – Charging or discharging
Patent
1993-10-18
1996-06-04
Hoang, Tu
Industrial electric heating furnaces
Arc furnace device
Charging or discharging
373 84, 266 45, F27D 314
Patent
active
055241190
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to an improved apparatus and method for pouring molten metal from a furnace or converter, and more particularly to an improved furnace or converter tap hole design.
BACKGROUND ART
Tilting electric arc furnaces, for example as used in steel manufacture, are provided with a taphole through which an oxygen lance can be inserted and from which the molten metal passes when the furnace is tilted at the end of the melting process. Traditionally the molten metal is poured into a trough, or launder, accompanied by a quantity of slag which becomes unavoidably entrained in the metal stream. To overcome the problem of slag contamination, it has recently been proposed to provide the taphole with a hydraulically operated sliding gate valve mechanism which provides a positive shut-off for the metal stream at the end of the pouring step and effectively prevents the slag, which floats on the surface of the metal, from entering the ladle. Such a device is, for example, supplied by
Flogates Limited under the name FloCon Model 12800 Tap Hole Valve, and incorporates a collector nozzle.
The sliding gate taphole valve works well in practice, but, due to the extra length of taphole tube required to accommodate the valve mechanism and collector nozzle in certain types of furnaces, problems can arise due to turbulence in the metal stream, which adopts a jagged appearance and is difficult to pour accurately. Efforts to eliminate this problem have hitherto proved unsuccessful.
DISCLOSURE OF INVENTION
We have now discovered that an improved metal stream which is smoother and less turbulent can be produced by providing the taphole and/or collector nozzle with an offset bore enlargement. The reason for the improvement in flow is not entirely understood, but may result from an improved ability of dissolved gases to escape from the metal stream during its passage through the taphole tube and/or collector nozzle.
According to one aspect of the present invention there is provided a tilting electric arc furnace or converter having a taphole and/or collector nozzle which is provided, for at least a portion of its length, with an offset bore enlargement.
The invention also comprises a method of pouring molten metal from a tilting electric arc furnace or converter, in which the metal is discharged through a taphole and/or collector nozzle which is provided, for at least a portion of its length, with an offset bore enlargement.
In another aspect, the invention also provides a sliding gate taphole valve provided with a collector nozzle, the collector nozzle being provided, for at least a portion of its length, with an offset bore enlargement, a collector nozzle having an offset bore enlargement for use therewith, and a gate set incorporating such a collector nozzle.
Although it is envisaged that the principle of the offset bore enlargement could be applied to the taphole itself, to the collector nozzle, or to both the taphole and the collector nozzle, it is usually simpler and more convenient to form the offset bore enlargement solely in the bore of the collector nozzle. The invention will thus be further exemplified with respect to such a collector nozzle having an offset bore enlargement but is not to be taken as limited thereto.
The collector nozzle can be fixed immovably to the furnace or converter but is preferably attached to the sliding gate of a sliding gate valve mechanism of the type previously mentioned.
The enlargement to the collector nozzle bore is offset from the central line of the bore and is usually, though not necessarily exclusively, an enlargement to the vertical height of the bore. Other directions of the enlargement may also be possible, and the invention also includes the possibility of more than one such enlargement offset in different and possibly opposite directions from the central line. However, preferably the height of the bore is greater than the width, and for example the bore may be of ovoid, elliptical or any other suitable non-circular cross-sectional shape. Preferab
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Flo-Con Systems, Inc., "Flo-con Model 12800 Tap Hole Valve", 1983 (copyright date) pp. 1-5.
Forgemasters Steels Limited
Hoang Tu
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