Industrial electric heating furnaces – Arc furnace device – Plural furnace units
Reexamination Certificate
2000-05-17
2001-07-31
Hoang, Tu Ba (Department: 3742)
Industrial electric heating furnaces
Arc furnace device
Plural furnace units
C373S081000, C373S084000, C266S045000
Reexamination Certificate
active
06269112
ABSTRACT:
TECHNICAL FIELD
This invention relates to an electric arc furnace and process for the continuous charging and melting of ferrous material and its alloys and for the semicontinuous tapping of molten steel from the furnace.
BACKGROUND OF THE INVENTION
Electric arc furnaces that can be continuously charged with scrap and from which molten steel can be semicontinuously tapped are known in the iron and steel industry. In these furnaces, the charge can be fed continuously by means of a conveyor belt, a revolving drum or buckets. When buckets are used, they are often filled with scrap in a separate area and transported to the furnace in a semicontinuous charging mode called “batch charging.” It is also known to use multiple furnaces or melt zones for continuous charging in an efficient manner, as in U.S. Pat. No. 5,602,867 to Hubers et al., U.S. Pat. No. 3,783,169 to Newhall, and U.S. Pat. No. 3,379,815 to Parker.
These known electric arc furnaces which operate with a continuous scrap supply either tilt or use tilting devices to completely empty the furnace vessels between heats. A tiltable arc furnace that tilts in one direction to pour molten charge and in the opposite direction to remove slag is shown in U.S. Pat. No. 2,886,617 to Sorg et al. Tilting furnaces are also shown, for example, in U.S. Pat. No. 5,462,259 to Guido and U.S. Pat. No. 2,783,990 to Tripmacher et al.
One limitation of the technologies currently available for continuous melting is that scrap in the bottom part of the furnace is always in contact with the molten steel to be tapped, and therefore the overlying molten, refined steel layer may be polluted by the underlying scrap being melted. This can lead to off-specification product. Another limitation is that the composition and the temperature of the molten steel to be tapped cannot be accurately monitored, which also can cause quality problems. A third limitation is that the melting zone and the refining zone are full of solid and incompletely melted scrap which can clog the tapping hole and spill molten steel with the attendant loss of time and energy. To overcome these problems, the process must be temporarily stopped and the melting operation must be turned off in order to tap the molten steel. What is needed to overcome these deficiencies is a furnace with vessels which can be continuously charged and then tapped from side to side without interrupting the charging and the melting of incoming charge, and without emptying the entire furnace vessel between heats.
SUMMARY OF THE INVENTION
Our invention makes possible the continuous melting of ferrous materials such as sponge iron, scrap iron or iron ore in an electric arc furnace so that the electric arc is never turned off nor is the power ever reduced. The invention also allows the semicontinuous tapping of molten steel from the furnace. This invention assures the continuous melting of ferrous materials, which can be preheated along a feeding duct, the simultaneous and continuous refining of molten steel by a means that prevents contamination from the metal charge and eliminates the danger of clogging the tapping hole, and the semicontinuous tapping of molten steel when it is adequately refined.
Our invention comprises an electric arc furnace for continuous charging of ferrous materials and semicontinuous tapping of molten steel, comprising (a) a body, having a central melting zone and at least two lateral shafts adjacent to the central melting zone, the base of said central melting zone being higher in elevation than the bases of the lateral shafts; (b) a roof over the body; (c) a central stack extending vertically from the roof above said central melting zone, the central stack having a means for charging ferrous materials into the central melting zone, having a means for removing exhaust gases from the central melting zone and having a pivot point located below the means for charging; (d) a means for melting material charged into the furnace; (e) a means for tapping molten steel from the furnace; (f) a means for injecting refining aids into the lateral shafts; (g) at least one deslagging door positioned within the body; and (h) a means for tilting the furnace to alternatively tap the lateral shafts. The lateral shafts act alternatively as containers for the molten steel and as vessels for the refining process. These two functions can be interchanged without shutting down the furnace. A means for tilting the furnace about a vertical axis allows for the tapping of steel alternatively from either lateral shaft and from the central melting zone if so desired. The oscillating stroke is small, but sufficient to convey the molten steel into a lateral shaft while at the same time to allow the refining process to be carried out in the alternate lateral shaft until the steel is tapped. Deslagging occurs through a side door of the furnace body.
According to another feature of the invention, the electric arc furnace is fitted with a means to supply electrical energy, oxygen and additives. The melting process includes the use of injecting lances for fuel and combustent gases, such as oxygen, with a high-density jet, and a means to seal the furnace electrode openings.
Optionally, our invention can also charge molten metal directly into the refining shafts. It can be used as a ladle furnace to correct the final steel analysis, thus eliminating the present need for a refining phase in the ladle station of steelmaking plants.
REFERENCES:
patent: 2783990 (1957-03-01), Tripmacher et al.
patent: 4740989 (1988-04-01), Steipe et al.
patent: 5462259 (1995-10-01), Guido
patent: 5535235 (1996-07-01), Ao et al.
Benedetti Gianpietro
Losciale Matteo Vittorio
Pavlicevic Milorad
Poloni Alfredo
Garber Kevin J.
Hoang Tu Ba
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