Metal founding – Means to shape metallic material – Continuous or semicontinuous casting
Reexamination Certificate
1999-06-11
2001-05-29
Lin, Kuang Y. (Department: 1722)
Metal founding
Means to shape metallic material
Continuous or semicontinuous casting
C164S480000
Reexamination Certificate
active
06237673
ABSTRACT:
BACKGROUND 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.
In a twin roll caster molten metal is introduced between a pair of contract-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.
The setting up and adjustment of the casting rolls and the metal delivery and pool confinement components 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. The rolls may need to be changed between casts so as to allow a different width of strip to be cast and the rolls must be replaced if the casting surfaces are in any way damaged or deteriorate during casting. If the rolls have to be changed in sit-up, a significant amount of potential casting time is lost waiting for the casting components and the area surrounding them to cool. The new set of rolls, once in place, have to be calibrated prior to casting so that the nip width can be pre-set. When casting ferrous metals, it is necessary to preheat the refractory components of the metal delivery and pool confinement means to very high temperatures before casting commences. For these reasons it has been proposed to build twin roll casters with demonstrable components so that the rolls and preheated refractory components can be rapidly brought together into an operative assembly and casting started before the preheated components cool significantly. One example of a caster with moveable rolls and refractory components is disclosed in our Australian Patents 631728 and 637548 and corresponding U.S. Pat. Nos. 5,184,668 and 5,277,243.
The invention described in our Australian Patent Application 84244/98 enables a twin roll strip caster to be built with a modular construction in which the casting rolls are installed in a moveable module readily moveable into and out of the machine and in which the rolls can be accurately set up in the module so that the nip is preset and will be located accurately in the machine when the module is installed. This enables roll sets to be set up in advance in replacement modules for rapid changing of rolls between casts. However, proper positioning of the pool confinement side dams and proper adjustment of the mechanisms to apply the side dams to the ends of the rolls remains a problem, particularly if the size of the rolls is changed to allow a different width of strip to be cast.
A change of strip width requires a similar change in the width of the metal delivery nozzle and there must be an appropriate repositioning of the supports for the nozzle. There will generally also be a need to reposition other components which are dependent on the width of the casting pool, for example, any sealing elements which seal the casting pool chamber and any pool level sensor or camera installed at an end of the pool to examine the pool conditions during casting.
By the present invention the side dams and side dam applicators are mounted on a pair of carriages which can be moved in and out and preset to positions appropriate to the width of the casting pool. The side dams can thus be rapidly repositioned when the rolls are changed for any reason, for example, for a change of width of the strip to be cast. Moreover, the carriages can also be used to support other components which need to be adjusted according to the width of the casting pool, for example, nozzle end supports, casting pool seals and camera mountings.
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; a pair of pool side plates to engage end surfaces of the rolls whereby to form side confining closures for the casting pool; a pair of side plate holders to hold the side plates; a pair of generally horizontally acting thrusters connected to the side plate holders and actuable to apply opposing inward closure forces to the side plates; 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 the thrusters are mounted on a pair of carriages disposed one at each end of the casting roll assembly and moveable toward and away from one another to enable the spacing between them to be adjusted so that the carriages can be preset before a casting operation to suit the width of the casting rolls and to allow them to serve as reaction abutments against which the thrusters react to apply the inward closure forces to the side plates and wherein further both carriages are mounted on a central frame structure which sits over the casting rolls.
Preferably, the metal delivery means comprises an elongate metal delivery nozzle disposed immediately above the nip and a metal distribution vessel to distribute metal into the nozzle. The metal delivery nozzle may be composed of two or more pieces disposed end to end.
Preferably further, the frame structure provides a central nozzle locating support for the metal delivery nozzle.
Preferably further, there is a carriage drive means acting between the frame and the carriages to move the carriages toward and away from one another.
Preferably further, the carriage drive means is operable to set the carriages at any one of a plurality of preset spacings in which they are set generally equidistant from the central nozzle locating support.
Preferably further, the carriages are provided with nozzle outer end supports to support outer ends of the nozzle at locations the spacing of which is determined by the preset spacing of the carriages.
Preferably too, the nozzle outer end supports are mounted on the carriages so as to be equidistant from the centre nozzle locating support when the carriages are in any of their preset spacings.
The carriages may also be provided with sealing means to engage the metal delivery means so as to provide a sealed casting pool chamber above the casting pool. Where the metal delivery means comprises a metal distribution vessel disposed above a delivery nozzle, the sealing means may engage end parts of the distribution vessel.
At least one of the carriages may also be provided with a camera mounting for mounting a camera to observe the casting pool during casting whereby to maintain a generally constant relationship between the camera position and the respective pool confining side dam.
Preferably, the camera mounting is positioned directly above the respective side dam structure.
REFERENCES:
patent: 5810070 (1998-09-01), Osada et al.
Fish John Andrew
Kato Heiji
Russell Wayne
Ishikawajima-Harima Heavy Industries Company Limited
Kerins John C.
Lin Kuang Y.
Miles & Stockbridge P.C.
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