Method and apparatus for electromagnetic confinement of molten metal in horizontal casting systems

Abstract

The present invention provides an apparatus for strip casting of molten metal including a pair of casting rollers adapted to receive molten metal along a horizontal axis, wherein a vertical distance separating the pair of casting rollers defines a molding zone; and an electromagnetic edge containment apparatus positioned on each side of the molding zone having an induction coil wound about a portion of a magnetic member to generate magnetic lines of force upon application of a current, wherein the poles of the magnetic member are positioned distal from to aligned to the planar sidewall of the casting rollers and the current provides magnetic lines of force perpendicular to said horizontal axis that contain the molten metal in contact to the casting rollers without substantially increasing the temperature of the molten metal.

Description

FIELD OF THE INVENTION [0001] The present invention relates to the continuous casting of metal strip, and more particularly, to the electromagnetic confinement of molten metal in a continuous casting system. BACKGROUND OF THE INVENTION [0002] Continuous casting of metals is performed in twin-roll casters and belt casters or combinations thereof. Methods are available for casting both in the horizontal and in the vertical direction. In particular, the steel industry has recently developed high speed twin roll strip casters which operate in the vertically down direction. [0003] Up to the present, the mechanical edge dams have been employed to provide containment of the molten metal in the casting zone. Such devices have included the caterpillar type edge dams that move with the strip (as in the Hazelett casters) or fixed edge dams that are pressed against the surface of the rolls. The latter is used in the twin-roll steel strip casting industry. Such fixed mechanical edge dams have a ...

AI Technical Summary

Benefits of technology

[0015] (c) a means for supplying the molten metal to the molding zone along said horizontal axis from a tundish while ensuring said molten metal remains substantially non-oxidized, wherein the tundish is separated from the molding zone by a distance to substantially eliminate wave generation within the tundish by the magnetic lines of force.

[0026] (c) a means for supplying said molten metal to the molding zone along a horizontal axis from a tundish, the tundish separated from said molding zone by a distance to substantially eliminate wave generation within the tundish by the magnetic lines of force.

Problems solved by technology

Such fixed mechanical edge dams have a short service life as they get eroded by contact with the cold sidewall of the rolls.

In addition, such mechanical edge dams provide sites for the formation of skulls that have a tendency to be sheared off and thus enter the cast strip to render the microstructure metallurgically undesirable.

Caterpillar edge dams, while well proven for the thicker slab castings (10-25 mm thick), become impractical for thin strip casters or twin drum casters of the steel industry where the cross section to be contained changes sharply along the casting zone.

However, such systems are not without disadvantages.

For example, such systems typically have poor operating efficiency resulting from core losses and losses due to magnetic hysterisis when an alternating magnetic field is applied to the magnetic material.

However, induction systems are disadvantageously limited in terms of the maximum metallostatic head that can be contained by the system.

The maximum metallostatic head that can be supported in induction coil systems is limited, because induction coil systems require very high inductor currents to provide adequate containment forces, wherein such high currents are accompanied by increased heat generation, which in turn hinders or slows the solidification process during casting.

Such electromagnetic edge dams have not been successfully commercialized for two reasons.

First, the high current required to contain the molten metal pool creates standing waves on the top surface of the metal pool that are too large in magnitude for the casting process.

Second, the large electromagnetic forces needed to contain the molten metal head formed atop vertical roller caster systems create induction heating on the metal pool's sidewall, which interferes with the solidification process.

In addition to induction heating and wave generation, the rim portions of the casting rolls disclosed in U.S. Pat. No. 4,936,374 produce a ridge in the cast product and therefore fail to provide a casting strip having uniform sidewalls (edges).

Additional machining disadvantageously adds to the cost of the production.

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