Metal founding – Process – Shaping liquid metal against a forming surface
Patent
1996-10-03
1998-11-17
Ryan, Patrick
Metal founding
Process
Shaping liquid metal against a forming surface
164475, 164479, 164414, 164429, 164444, B22D 11124, B22D 1106
Patent
active
058363777
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a process an apparatus for cooling molten steel, particularly continuous casting, in which at least a portion of the molten metal that emerges from a nozzle of a metallurgical vessel is solidified by means of contact with a cooling surface.
BACKGROUND OF THE INVENTION
In continuous or strand casting, the molten metal is directed into a cooled mold. Contact with the cooling mold causes a solidification front to form, beginning at the outside and moving toward the interior of the strand. In order to improve the quality of the metal blanks, it is known to supply them with an inert gas.
For example, German Patent Publication DE OS 21 63 928 proposes that during the production of steel blanks by means of the continuous casting of a metal stream into a cooled mold, an inert gas be introduced over the metal at the upper part of the mold in the vicinity of the surface of the molten metal. The use of nitrogen or argon that has previously been liquified by compression and lowered temperature, which is applied in liquified state to the surface of the steel blanks, is suggested. The aforementioned document merely discloses exposing the molten metal to an inert gaseous atmosphere and directing the gaseous jet in such a way that the molten metal of the blanks is offset around a vertical axis in a rotational movement.
From German Patent Publication DE 32 27 132 A1, it is known to surround a metal stream that emerges from a metering nozzle with a protective mantle of inert gas, e.g.; argon or nitrogen, in order to keep air away from the vicinity of the metal melt. This pressurized inert gas screens off the oxygen coming from the ambient air and in this way prevents reoxidation of the exposed metal melt meniscus. The expert in this document does not undertake more extensive influencing of the molten metal. Furthermore, the use of inert gas to treat metal strands or wires that are solidified already or only heated is known. For example, in German Patent Publication DE 35 06 597A1 a wire is exposed to a lightly reducing gas in the housing of a cooling column. The gas used in this case is supplied to the housing in an undirected fashion and serves exclusively to cool and, usually, to reduce scale formation. In the cited casting processes, the inert gas is brought into contact with the molten or the already solidified surface. In the case of continuous casting as known from German Patent Publication DE 38 10 302, for example, the molten metal is deposited on a cooled continuous belt and the exposed surface of the strand cools during its transport on the belt, so that the exposed surface in the front area near the nozzle is still molten and solidifies later due to cooling.
SUMMARY OF THE INVENTION
An object of the invention is to create a process and a corresponding device that can influence the surface of a continuously cast metal strand in respect to both its form and its quality.
According to the invention, a gaseous stream is directed onto the surface of a freely accessible molten steel strand directly after the latter emerges from a metal nozzle of a metallurgical vessel. The surface of the strand is thereby exposed to a gas that forms an inert atmosphere at least until the steel strand solidifies completely. Along with gases low in oxygen, e.g. flue gas, inert gases such as argon or nitrogen, in particular, can be used.
The use of these gases intensely influences the surface of the steel strand; specifically, in the molten area as well as in the solidified area and the area of molten/solid transition. As a result, scaling is avoided. Furthermore, using the gas in the vicinity of the nozzle allows deliberate influence to be exercised on the heat extraction and surface tension. Depending on the desired quality of the steel strand or steel strip, the inventors propose to either heat the gas and in this way prevent solidification of the strand surface for a predeterminable segment or, in another embodiment, to cool the gas to such an extent that it is transported
REFERENCES:
patent: 5299628 (1994-04-01), Ashok
Freier Paul
Reichelt Wolfgang
Spitzer Karl-Heinz
Urlau Ulrich
Lin I.-H.
Mannesmann Aktiengesellschaft
Ryan Patrick
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