Dispensing – Molten metal dispensing – With subjacent flow guide
Reexamination Certificate
1998-12-04
2001-05-08
Kastler, Scott (Department: 1742)
Dispensing
Molten metal dispensing
With subjacent flow guide
Reexamination Certificate
active
06227421
ABSTRACT:
The present invention concerns a continuous casting tundish for a steel mill, equipped with at least one tube changer, this changer being comprised of a chassis mounted on the tundish, refractory pieces that delimit a pouring channel for passage of the steel from the tundish to a continuous casting mold, those refractory pieces being comprised of at least one fixed plate and a tube having a plate at its upper end, means for exerting pressure for applying the plate of the tube against the fixed plate, their surfaces forming a junction plane, a position for introducing a new tube, a casting position and a position for evacuating a worn tube, guidance means that permit the new tube to pass from the introduction position to the casting position and the worn tube to pass from the casting position to the evacuation position, actuating means for passing the new tube from the introduction position to the casting position and the worn tube from the casting position to the evacuation position.
An example of such a device is described in the French patent application registered under N° 95 05 504. This device presents advantages over the other existing devices, as described for example in the document EP 0 192 019. However, it has the shortcoming of requiring cylindrical sliding surfaces for the fixed plate and for the tube plate. To guarantee a good tightness of the plates, it is necessary that the radii of the fixed plates and the tube plate be absolutely identical, which involves difficulties in machining. Furthermore, these plates are subject to thermal stresses during casting and it is not certain that the deformations caused by their thermal expansion are identical over the entire periphery of the plates, which can cause a lack of tightness between these plates. It is also known that the pouring channel in such a device is generally under a lower pressure than atmospheric pressure. To avoid any aspiration of air that would cause a chemical perturbation and degradation of the steel quality. at least one groove that runs completely around the pouring channel is generally provided in one of the fixed of mobile plates, this groove being supplied with a neutral gas under pressure, such as argon for example, such that any aspiration is that of neutral gas that does not cause a chemical degradation of the steel. The machining of such grooves on cylindrical plates proves extremely difficult and costly.
The present invention concerns a tundish equipped with a tube changer that has the same advantages as the device described above but not the disadvantages.
According to the principal characteristic of the invention, the junction plane is inclined at a nonzero angle (&agr;) relative to the horizontal; the new tube passes from the introduction position to the casting position and the worn tube from the casting position to the evacuation position by a sliding movement on the junction plane following a trajectory at least partially not rectilinear, the combination of the angle of inclination (&agr;) of the junction plane, the dimensions and the trajectories of the tubes being such that the tubes avoid the casting mold during a tube change.
The combination of an inclined junction plane and a nonlinear movement makes it possible to predetermine within a broad range the original and the final positions of the tubes, an advantage the importance of which will be understood better in the following descriptions.
According to a preferred characteristic of the invention, the plates of the tubes have a front support face and a rear support face, the front and rear faces being defiled with respect to the direction of tube change, the front support face of the new tube plate coming in contact with the rear support face of the worn tube plate to push it toward the evacuation position and replace it in the casting position.
According to another preferred characteristic of the invention, the continuous casting mold has a larger dimension and a horizontal straight line of the junction plane is parallel to this larger dimension of the mold. This offers the maximum displacement possible of the tube inside of the mold.
According to another preferred embodiment, the tube change is effected along a circular sliding movement of center O in the junction plane. A rotation in effect offers the advantage of being extremely easy to effect mechanically.
According to a particular embodiment of the invention, the center O of the circular movement is higher than the level where the pouring channel passes through the junction plane. This configuration makes it possible to introduce a new tube outside of the mold and to introduce it by rotation to the inside of the mold while the tube in service situated inside the mold is removed from the mold during the exchange rotation. This configuration is adapted more particularly to molds for slabs, the shape of which is elongated, and which permit movements of the tube longitudinally inside of the mold.
According to another particular implementation form of the invention, the center O of the circular movement is lower than the level where the pouring channel passes through the junction plane. This configuration is particularly adapted for bloom molds, the section of which is square or nearly square. In such molds the changing of an immersed tube without raising the tundish implies that a new tube could be prepositioned alongside the tube in service. Considering the narrowness of the mold, this implies that the new tube is inclined so that its end is in the immediate vicinity of the end of the tube in service at the center of the mold.
According to another particular embodiment, the junction plane between the fixed plate and the tube plate is vertical. The vertical plane is preferably parallel to the major axis of the mold. This configuration, which guarantees tube movements perfectly aligned with the major axis of the mold is particularly adapted for molds for thin slabs.
According to another particular embodiment, the tube changer is located on the side on the tundish instead of being placed under the tundish as is generally done. This configuration permits suppressing a bend in the pouring channel. It also makes a free space available above the tube changer for the mechanical operations. In the continuous casting of steel, a device for regulating the flow of steel, e.g., a stopper rod or a slide valve, is generally used. The present invention offers new possibilities for combining the tube and the slide valve closure device. In particular, according to one embodiment. the tundish is equipped with a slide gate between it and the tube changer.
According to another particular embodiment, the plates of the tubes have rectilinear support faces, these support faces being inscribed in a sector of center O and with an angle to the center equal to the angle of rotation of the plates during a tube change. This configuration permits two tube plates to be pushed during the exchange without ever allowing any play between their support face when the sliding movement on the junction plane is a rotation.
When the sliding movement is not entirely a rotation, the tube plates preferably have support faces in the form of concave and convex arcs of a circle, the front support face of a plate being adapted to the rear support face that precedes it, the support faces remaining in contact over a sufficient distance to completely cover the pouring orifice at least when the support faces traverse the orifice of the fixed plate during the tube change. This configuration permits two plates/tubes to be pushed during the exchange while permanently closing off the pouring orifice.
In a tube changing system the pouring channel is normally perpendicular to the junction plane between the fixed plate and the mobile plate. When this junction plane is vertical or close to vertical, it implies that the pouring channel has the form of a bayonet between the upper container and the entrance into the fixed plate. This bayonet form of the pouring channel can present disadvantages. On the one hand, the wear of the pouring cha
Abels Hubert
Richard Francois-Noel
Kastler Scott
Vesuvius Crucible Company
Williams James R.
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