Metal founding – Including means to directly apply magnetic force to work or... – By electromagnetic means
Patent
1997-03-17
1998-04-21
Lin, Kuang Y.
Metal founding
Including means to directly apply magnetic force to work or...
By electromagnetic means
164466, B22D 2702
Patent
active
057408556
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a device for slowing down the non-solidified portions of a cast strand during continuous casting of billets or blooms. The device comprises a plurality of moulds which are open in the direction of casting. The moulds are arranged to be supplied each with a flow of melt. The device comprises at least one member for generating a static magnetic flux or a periodic low-frequency magnetic flux to act in the path of the inflowing melt in such a way that the movement of the melt is slowed down, and a plurality of magnetic core parts arranged to form a closed magnetic circuit together with the moulds.
BACKGROUND OF THE INVENTION
During continuous casting, hot melt flows into a mould which is open in the direction of casting. In the mould the melt is cooled so as to form a solidified, self-supporting surface layer before the cast strand leaves the mould. If inflowing melt is allowed to flow into the mould in an uncontrolled manner, it will penetrate deep down into the non-solidified portions of the cast strand. This renders difficult the separation of unwanted particles contained in the melt. In addition, the self-supporting surface layer is weakened, which increases the risk of melt breaking through the surface layer formed in the mould.
It is previously known to arrange one or more static magnetic fields or periodic low-frequency magnetic fields in the path of the melt to slow down and distribute the inflowing melt and to prevent deposits of unwanted particles, or melting on the inside of the solidified shell, or other drawbacks. The static magnetic field or the periodic low-frequency magnetic field is generated by means of magnets, which, for example, may consist of permanent magnets or coils with magnetic cores, supplied with current.
To slow down the incoming melt during casting of slabs, that is, sheet blanks, usually one or more magnets are arranged on two opposite sides of the strand, and the magnetic flux is returned via an outer return conductor arranged between the magnets. From Swedish patent specification 8604456-7, corresponding to U.S. Pat. No. 4,986,340 a device for slowing down a flow entering a mould, which is divided for the purpose of obtaining two separate cast strands, is previously known. The cast strands are separated by means of an intermediate section, for example a cooled copper body. On either side of the divided mould, a magnet is arranged in the form of a coil and a core. The magnets are arranged such that both mould parts are included in a common magnetic circuit and the mould parts are placed in series with each other.
A device for casting billets or blooms, that is, wire blanks or tube blanks, usually comprises several moulds. A device for casting billets normally comprises between four and eight moulds. Arranging for each mould, in the same way as for slabs, at least one magnet on each of two opposite sides of the strand, and then returning the magnetic flux via an outer return conductor arranged between the magnets, is both costly and space-demanding and is therefore not applicable to casting devices comprising more than two moulds.
Since there is normally a shortage of space in the casting device, it is important that the magnets be as small as possible. The closer to the mould a magnet is placed, the smaller it needs to be, due to the leakage flux becoming smaller. If the magnet is placed some distance away from the mould, it must be made stronger to compensate for the leakage flux if the same magnetic flux is to be obtained in the mould. The fact that the core becomes saturated at a certain magnetic flux puts a lower limit to the size of the core. A stronger magnet therefore needs a larger core to avoid that the core becomes saturated. In the above-mentioned divided mould, the separated moulds share two magnets. If two separate moulds placed somewhat spaced-apart are arranged with magnets in a corresponding way, the distance between the mould and the magnet becomes so large that the leakage flux causes the magnets to be stron
REFERENCES:
patent: 4986340 (1991-01-01), Eriksson
Eriksson Jan Erik
Hallefalt Magnus
Kollberg Sten
Lehman Anders
Asea Brown Boveri AB
Lin Kuang Y.
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