Metal founding – Means to shape metallic material – Continuous or semicontinuous casting
Reissue Patent
1998-12-17
2001-06-12
Lin, Kuang Y. (Department: 1722)
Metal founding
Means to shape metallic material
Continuous or semicontinuous casting
C164S480000
Reissue Patent
active
RE037214
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to continuous casting of thin metal products, in particular thin steel strips, according to the continuous casting technique between two cooled counter-rotatory rolls. It more particularly relates to side dams applied against the front ends of the rolls in order to delimit the casting space defined between the rolls, as well as the means for supporting them and applying them against the side front ends.
BACKGROUND OF THE INVENTION
It is known that installations for continuous casting between rolls include two rolls with horizontal and parallel axes, vigorously cooled internally by circulation of water driven in rotation in opposite directions and spaced apart by a distance corresponding to the desired thickness of the cast product.
During casting, molten metal poured into the casting space defined between the rolls solidifies in contact with these rolls and is extracted downwards, as the rolls rotate, in the form of a thin strip. In order to contain molten metal, the side dams are pressed flat against the front ends of the rolls. Such side dams are commonly made of refractory material, at least in the part of the dam which is brought into contact with the molten metal.
It is therefore necessary to ensure leaktightness between the rolls and the side dams. For this purpose, these side dams are pressed against the ends of the rolls and, in order to reduce the friction induced during rotation of the rolls, lubrication of the interface between the rolls and side dams is usually provided. Lubrication is carried out by supplying a consumable lubricant or by using a self-lubricating material at this interface.
However, actually producing this leaktightness and retaining it throughout the casting still raises numerous difficulties, due in particular:
to the geometrical deformations of the rolls and of the side dams, in particular at the start of casting, which are caused by expansions of the various elements of the installation,
to the forces exerted on these elements in particular the forces exerted on the side dams by the cast metal in the axial direction of the rolls, which forces tend to separate the side dams from the rolls,
to wear of the side dams or of the edges of the cooled walls of the rolls, which is not always uniform over the entire area of the contact zones,
to the possible beginning of infiltration of cast metal between side dam and roll, and solidification of these infiltrations which tends to separate one from the other.
It has already been proposed to solve these problems by causing controlled wear of the side dam, by friction of the rolls against the latter, throughout the casting. The aim is thus to regenerate the interface between rolls and side dams continuously, so as to make the contact conditions over the entire area of this interface as uniform as possible. Thus, document EP-A-546,206 describes a method according to which, before the start of casting, the side dams are pressed strongly against the rolls, in order to carry out a sort of grinding-in of these side dams by abrasion by the edges of the rolls. Then this pressure is reduced and, during casting, the side dams are continued to be moved towards the rolls at a predetermined speed in order continuously to ensure the progress of intentional wear and thus to attempt to retain uniform contact over the entire area of the interfaces.
However, this method leads to a significant wear of the refractory material of the side dams, even when the contact conditions are satisfactory.
If, instead of regenerating the interface as indicated above, the side dam is merely applied with a predetermined force, stronger wear may occur in certain zones of the interface, or in other zones of localized infiltration between the edge of the rolls and the side dam, which lead to local creation of play between the roll and the side dam. For example, an infiltration of molten metal between a roll and a side dam will tend, by solidifying, to separate the side dam from the edge of the roll, and therefore also from the edge of the second roll, since the entire side dam will then be displaced backwards, with the risk of deteriorating the leaktightness at the second roll. The same problem may occur if the front end of the rolls are not perfectly orthogonal to the axes of the rolls and/or are not exactly in the same plane; in this case, the side dam is correctly applied against one roll but not against the other.
SUMMARY OF THE INVENTION
The object of the present invention is to solve these problems, and aims in particular to maintain the best possible leaktightness, throughout casting, between a side dam and the two rolls against which it is applied.
With these objects in mind, the subject of the invention is a device for continuous casting of thin metal products between rolls, including two cooled counter-rotatory rolls, two side dams and means for supporting and applying by pressure the side dams against the edges of the rolls, characterized in that the support means include:
a thrust plate which can be moved in the axial direction of the rolls and which is arranged perpendicular to this direction,
a panel, which supports the side dam and which is carried by the thrust plate and arranged facing the latter,
at least three thrust members interposed between the thrust plate and the said panel, these members being distributed over a zone of shape corresponding to that of the side dam, and being capable of exerting thereon thrust forces independently of one another.
The panel is only supported by the thrust plate, that is to say that it is mechanically connected to it only in the vertical direction and optionally horizontally, perpendicularly to the axes of the rolls. On the other hand, the panel may be displaced with respect to the thrust plate, on the one hand in the direction of the axes of the rolls and, on the other hand, by pivoting with respect to it about any axis located in the overall plane of the panel, substantially orthogonal to the axial direction.
These various allowed displacements are, of course, limited in amplitude, but are sufficient to allow the side dam to be applied in the best possible manner against the front ends of the rolls, even if the respective front ends of the rolls are not perfectly coplanar. In addition, when the side dam is caused during casting to be separated from the edge of a roll, for example following passage of a parasitic solidification of the cast metal between this roll and the side dam, the latter can pivot slightly on itself and therefore retain the best possible contact with the second roll. Without this freedom of movement, such a parasitic solidification would lead to pushing back the side dam in its entirety and to creating play between the latter and the second roll.
Furthermore, during such pivoting, the thrust members located on the side where the side dam moves away from the roll are more greatly stressed and, by reaction, it is possible to act preferentially or solely on them without substantially altering the thrust on the side of the second roll.
The thrust members may be controlled jacks or springs.
In the case in which the thrust members are jacks, they can then be controlled individually either in pressure or in displacement, which makes it possible to apply a stronger thrust just at the location where such an increase in thrust is required, for example in the case indicated above, on the side where parasitic solidification has taken place.
In the case in which the thrust members are springs, this increase in thrust is actually generated automatically by the compression of the springs, on the side where the side dam is moved away from the rolls, and therefore by increasing the force exerted by the pressed springs, insofar as the position of the thrust plate is fixed.
Preferably, the stiffness of each spring and the distribution of the springs in the zone are determined so that, for the same flexion of these springs, the thrust force which they exert in the lower part of the side dam is greater than the thrust force exerted in t
Barbe Jacques
Delassus Pierre
Vendeville Luc
Lin Kuang Y.
Nilles & Nilles S.C.
Usinor
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