Metal founding – Means to shape metallic material – Continuous or semicontinuous casting
Utility Patent
1998-09-16
2001-01-02
Lin, Kuang Y. (Department: 1722)
Metal founding
Means to shape metallic material
Continuous or semicontinuous casting
C164S480000, C072S246000
Utility Patent
active
06167943
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the casting of metal strip. It has particular application to the casting of metal strip by continuous casting in a twin roll caster.
2. Description of Related Art
In a twin roll caster molten metal is introduced between a pair of contra-rotated horizontal casting rolls which are cooled so that metal shells solidify on the moving roll surfaces and are brought together at the nip between them to produce a solidified strip product delivered downwardly from the nip between the rolls. The term “nip” is used herein to refer to the general region at which the rolls are closest together. The molten metal may be poured from a ladle into a smaller vessel or series of smaller vessels from which it flows through a metal delivery nozzle located above the nip so as to direct it into the nip between the rolls, so forming a casting pool of molten metal supported on the casting surfaces of the rolls immediately above the nip and extending along the length of the nip. This casting pool is usually confined between side plates or dams held in sliding engagement with end surfaces of the rolls so as to dam the two ends of the casting pool against outflow, although alternative means such as electromagnetic barriers have also been proposed.
The setting up and adjustment of the casting rolls in a twin roll caster is a significant problem. The rolls must be accurately set to properly define an appropriate width for the nip, generally the order of only a few millimeters, and there must also be some means for allowing at least one of the rolls to move outwardly against a biasing force to accommodate fluctuations in strip thickness particularly during start up. Previously proposed arrangements have employed roll mounting and biasing means in which require relative sliding movement between separate components at several locations, resulting in several sources of friction loading which interferes with accurate positioning of the rolls and accurate measurement of the roll biasing forces. The present invention provides a novel roll biasing system which minimises the sources of friction during operation.
SUMMARY OF THE INVENTION
According to the invention there is provided apparatus for continuously casting metal strip comprising a pair of parallel casting rolls forming a nip between them; metal delivery means to deliver molten metal into the nip between the rolls to form a casting pool of molten metal supported on casting roll surfaces immediately above the nip; pool confining means to confine the molten metal in the casting pool against outflow from the ends of the nip; and roll drive means to drive the casting rolls in counter-rotational directions to produce a solidified strip of metal delivered downwardly from the nip; wherein at least one of the casting rolls is mounted on a pair of moveable roll carriers which allow that one roll to move bodily toward and away from the other roll, wherein there is a pair of roll biasing units acting one on each of the pair of moveable roll carriers to bias said one roll bodily inwardly toward the other roll, and wherein each roll biasing unit comprises a thrust transmission structure connected to the respective roll carrier, a thrust reaction structure, compression spring means acting between spring abutments on the thrust reaction structure and the thrust transmission structure to exert a thrust on the thrust transmission structure and the respective roll carrier, and adjustment means operable to adjust the effective gap between the spring abutments thereby to adjust the thrust exerted by the spring means.
Preferably the adjustment means is operable to move the thrust reaction structure to alter its position relative to the thrust transmission structure.
Preferably further, the spring means is disposed within a barrel and the thrust transmission structure and thrust reaction structures are mounted on opposite ends of the barrel.
Preferably further, the thrust reaction means comprises a spring abutment member slidable in one end of the barrel and the adjustment means is operable to set the position of the spring abutment member in that end of the barrel.
The adjustment means may comprise a powered mechanical jack mounted on said one end of the barrel and operatively connected to the sliding reaction abutment. The jack may be a screw jack.
The thrust transmission structure may comprise a thrust transmission spring abutment slidable in the other end of the barrel.
The thrust transmission structure may incorporate a load cell to measure the thrust transmitted through it to the roll carrier.
The connection of the thrust transmission structure to the roll carrier may be releasable. In that case, the thrust transmission structure may be fitted with a clamping means to clamp the thrust transmission structure to the roll carrier.
The barrel may be moveable on a fixed support between an extended position to allow for connection of the thrust transmission structure to the roll carrier and a retracted position to enable the thrust transmission structure to be drawn away from the roll carrier when disconnected from it.
The compression spring means may be a helical spring housed within the barrel.
There may be adjustable stop means to limit inward bodily movement of said one roll toward the other.
The adjustable stop means may be disposed beneath the nip and between the roll carriers to serve as a spacer stop for engagement with the roll carriers to pre-set the minimum width of the nip between the rolls and adjustable in width to vary the minimum width of the nip.
The roll carriers may comprise a pair of roll end support structures for each of the rolls disposed generally beneath the ends of the respective roll. Each pair of roll end support structures may carry journal bearings mounting the respective roll ends for rotation about a central roll axis.
The adjustable stop means may comprise a pair of adjustable stops disposed one between each of the pairs of roll end supports at the two ends of the roll assembly.
The casting rolls and roll carriers may be mounted on a roll module installed in and removable from the caster as a unit. In that case, the thrust transmission structure of each biasing unit may be disconnectable from the respective roll carrier to enable the module to be removed without removing or dismantling the roll biasing units.
In apparatus in accordance with the invention both of the casting rolls may be biased by respective pairs of biasing units. Alternatively, one of the rolls may be restrained against lateral bodily movement and the other allowed to move laterally against either spring biasing forces or biasing forces in accordance with the invention.
REFERENCES:
patent: 2796781 (1957-06-01), Mills
patent: 4702300 (1987-10-01), Nakanori et al.
patent: 5706882 (1998-01-01), Fellus et al.
patent: 62-6740 (1987-01-01), None
patent: 1380816 (1988-03-01), None
Fish John Andrew
Kato Heiji
Ishikawajima-Harima Heavy Industries Company Limited
Kerins John C.
Lin Kuang Y.
Miles & Stockbridge P.C.
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