Specialized metallurgical processes – compositions for use therei – Processes – Electrothermic processes
Reexamination Certificate
1998-03-06
2001-05-22
Andrews, Melvyn (Department: 1742)
Specialized metallurgical processes, compositions for use therei
Processes
Electrothermic processes
C266S176000, C373S081000, C420S033000
Reexamination Certificate
active
06235075
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention is directed to a process for producing a high-silicon foundry pig iron and to a uniflow furnace with a centrally arranged electrode, which projects into the furnace vessel and is guided up to the vicinity of the base, and a counterelectrode arranged in the base of the furnace vessel for carrying out the process.
High-silicon foundry pig iron is an alloy of iron with about 3% carbon and up to 20% silicon. The iron alloy is smelted in foundries and has a silicon content for example of approximately 2.5%, in order to produce spun- or centrifugal-cast pipe which is principally used for water lines.
Foundry pig iron is usually smelted in a cupola furnace and the compostion is subsequently adjusted as appropriate by alloying with ferrosilicon. A disadvantage in this method is the high price of FeSi.
The object of the invention is to provide a process and corresponding apparatus in which the end alloy of the high-silicon foundry pig iron is smelted directly in a simple and economical manner.
SUMMARY OF THE INVENTION
This object is met by the invention.
In the invention, silicon oxides and iron-containing charge materials such as scrap, sponge iron, briquetted sponge iron, etc. and carbon-containing charge materials for reducing the silicon oxides and for carburizing are charged into a shaft furnace wherein the charge is guided through a ring shaft. The furnace interior is maintained under a highly reducing atmosphere, and the charge is melted by means of the radiation heat, especially by means of a transmitting or transferring arc.
Guiding the charge materials in a ring shaft prevents contact between the charge materials and the electrode. If the highly electrically conductive charge materials such as scrap, sponge iron, briquetted sponge iron and coal/coke were to contact the electrode, this would result in a short circuit and it would not be possible to supply the electrical power needed for the process. If an electrode is to be used, the material must be kept away from this heat source. As a result of the free space, the arc is maintained without hindrance between the graphite electrode and the molten bath. Due to the radiated energy of the arc, the charge materials pushed through the inner vessel to the edge of the furnace are melted and the energy required for the reduction of the silicon oxide is provided.
The melting process which is brought about by electrical energy is independent of the electrical conductivity of the charge materials as well as from its charging angle or angle of repose. Further, there are no special requirements with regard to the size of the charge materials. Thus, for example, the size of the usable scrap pieces is limited only by the clearance of the ring shaft.
In another embodiment of the invention, the silicon oxides are introduced directly and independently from the normal material column. The silicon oxide can be introduced into the furnace by a material lance through a hollow electrode. Accordingly, it is possible to melt exactly metered quantities of silicon oxide of sufficiently fine granulation in the shortest possible time. This silicon oxide condenses on the relatively cool coal located farther up the shaft. In so doing, it undergoes a transformation and is included in the melt as the charge continues to sink.
If separate feed means are not used for introducing the silicon oxide, the charge material is carefully mixed with the silicon oxide prior to introduction into the furnace;
In order to carry out the process, a low shaft furnace is used which has a ring shaft having a combustion space. The combustion space is maintained as an open volume during the entire process, allowing for the charge angle of the charge material, so that the radiant heat can be transferred to the material without hindrance.
Preferably, the inner shaft is of a conical construction so that the charge materials can be guided in the direction of the furnace base without interference. The size of the ring shaft is such that the charge materials are allowed to melt reliably.
In order to carry out the process, furnace vessel is closed and a highly reducing atmosphere is closed and maintained therein thus enabling the safe reduction of the silicon oxide. The silicon content of the charge materials can be up to 20%.
The following iron carriers are used: 80% shredder, 10% turnings, 5% tin cans, and 5% iron turnings.
The iron carriers mentioned above can be replaced in a further step by iron ore or sponge iron.
The various features of novelty which characterize the invention are pointed out with particularity in the claims appended to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects obtained by its use, reference should be had to the accompanying drawings and descriptive matter in which there is illustrated and described a preferred embodiment of the invention.
REFERENCES:
patent: 3919454 (1975-11-01), Langhammer
patent: 3985545 (1976-10-01), Kinoshita
patent: 5588982 (1996-12-01), Hendrix
patent: 2535284 (1975-08-01), None
patent: PCT/DE93/10348 (1994-05-01), None
patent: PCT/AU95/00563 (1995-09-01), None
Hofmann Werner
Reichelt Wolfgang
Andrews Melvyn
Cohen & Pontani, Lieberman & Pavane
Mannesmann Aktiengesellschaft
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