EP0698433B1 - Twin roll casting machine with applied side walls - Google Patents

Abstract

Device for the continuous casting between rolls of thin metal prods. comprises two cooled counter rotating rolls (1), two lateral obturation walls (3) and some means for supporting and pressing the obturation walls against the sides (2) of the rolls. The means of support comprises: (i) a thrust plate (10) that can move in the axial direction (A) of the rolls (1) and arranged perpendicular to this direction; and (ii) a platen (19) that supports the obturation wall (3), is carried by the thrust plate (10) and is arranged facing the plate. At least three thrust components (14) are interposed between the thrust plate (10) and the platen (19). These thrust components (14) are distributed in a zone corresponding to that of the obturation wall (3) and are able to exert independent pressing forces.

Description

The present invention relates to continuous casting thin metal products, especially strips thin steel, using continuous casting technique between two cooled counter-rotating cylinders. She relates more particularly to the obturation walls lateral, applied against the front ends of the cylinders, to delimit the casting space defined between the cylinders, as well as their support means and of application against said front ends.

It is known that casting installations continuous between cylinders have two axis cylinders horizontally and parallel, vigorously cooled internally by circulation of water, driven in opposite rotation, and spaced from each other a distance corresponding to the desired thickness of the cast product.

During casting, the molten metal is spilled in the casting space, defined between the cylinders, is solidifies on contact with them, and is extracted towards the bottom, when rotated, in the form of a thin strip. To contain the molten metal, the sealing walls side are pressed against the front ends cylinders. Such lateral closure walls are commonly made of refractory material, at less in their part brought into contact with the molten metal.

JP-A-63026243 and JP-A-57009565 describe lateral obturation walls whose support means include a movable push plate in the axial direction of the cylinders and arranged perpendicular to this direction, a plate supporting the closing wall and carried by the plate of thrust and arranged opposite it, and thrust members interposed between said plate thrust and said plate, and being able to exert thereon pushing forces independently of each other. The thrust force transmitted by the plate is applied only on the sealing wall. Document EP-A-212423 teaches that these pushing bodies can be constituted by actuated jacks, for example regulated in pressure.

It is therefore necessary to seal between the cylinders and the lateral closure walls. For this, these shutter walls are pressed against ends of cylinders. To reduce friction induced during the rotation of the cylinders, a lubrication of the cylinder-wall interface shutter is usually provided, this is carried out by adding a consumable lubricant or by use, at this interface, of a material self-lubricating.

• aux déformations géométriques des cylindres et des parois d'obturation, en particulier en début de coulée, provoquées par les dilatations des divers éléments de l'installation,
• aux efforts exercés sur ces éléments, notamment les efforts exercés sur les parois d'obturation, dans la direction des axes des cylindres, par le métal coulé, et qui tendent à écarter les dites parois d'obturation des cylindres,
• à l'usure des parois d'obturation, ou des chants des parois refroidis des cylindres, qui n'est pas toujours régulière sur toute la surface des zones en contact,
• aux éventuelles amorces d'infiltration de métal coulé entre paroi d'obturation et cylindre, et de solidification de ces infiltrations, qui tendent à les écarter l'une de l'autre.

However, the effective achievement of this seal and its conservation throughout the casting still presents many difficulties, due in particular to:

• to the geometric deformations of the cylinders and of the closure walls, in particular at the start of casting, caused by the expansions of the various elements of the installation,
• the forces exerted on these elements, in particular the forces exerted on the closure walls, in the direction of the axes of the cylinders, by the cast metal, and which tend to separate said closure walls of the cylinders,
• the wear of the sealing walls, or the edges of the cooled walls of the cylinders, which is not always regular over the entire surface of the areas in contact,
• to possible primers for the infiltration of metal poured between the closure wall and the cylinder, and for the solidification of these infiltrations, which tend to separate them from one another.

It has already been proposed to solve these problems by causing controlled wear of the closure wall, by friction of the cylinders against it, and this throughout the casting. So, we aim to regenerate by permanently the shutter wall - cylinder interface, so as to standardize the contact conditions as well as possible over the entire surface of this interface. So the document EP-A-546 206 describes a method according to which, before the start of the casting, we strongly press the shutter walls against the cylinders, to perform sort of a running-in of it by abrasion by the edges of the cylinders, then we reduce this pressure and, during casting, we continue to move the walls shutter to the cylinders at a speed predetermined to ensure continuation of voluntary usury and thus try to keep a regular contact over the entire surface of the interfaces.

But this method leads to significant wear refractory material from the end walls, even when the conditions of contact are satisfactory.

If, instead of regenerating the interface as indicated above, we just apply the wall shutter with a predetermined effort, it can produce greater wear in certain areas of the interface, or in other areas of infiltration located between the edge of the cylinders and the wall shutter, which lead to locally create a game between cylinder and end wall. For example, a infiltration between a cylinder and said wall goes tend, when solidifying, to spread the wall sealing the edge of this cylinder, and therefore also the edge of the second cylinder, since the wall then goes retreat as a whole, with the risk of deteriorating sealing at said second cylinder. The same problem can arise if the front walls cylinder ends are not perfectly orthogonal to the axes of the cylinders, and / or are not exactly in the same plane; in this case the wall shutter is properly applied against a cylinder but not against the other.

The object of the present invention is to resolve these problems, and in particular aims to keep the best possible sealing, throughout the casting, between a shutter wall and the two cylinders against which it is applied.

• une plaque de poussée mobile selon la direction axiale des cylindres et disposée perpendiculairement à cette direction,
• une platine, qui supporte la paroi d'obturation et qui est portée par la plaque de poussée et disposée en face de celle-ci,
• au moins trois organes de poussée interposés entre la dite plaque de poussée et la dite platine, ces organes étant répartis sur une zone de forme correspondant à celle de la paroi d'obturation, et pouvant exercer sur celle-ci des efforts de poussée indépendamment l'un de l'autre, la platine étant conformée de manière que l'effort de poussée qu'elle transmet soit appliqué uniquement sur la dite paroi, caractérisé en ce que, la paroi d'obturation étant constituée d'une plaque en matériau réfractaire dur entourée d'une ceinture métallique à laquelle elle est liée, la dite ceinture métallique est fixée sur une ceinture refroidie entourant une plaque en matériau réfractaire thermiquement isolant, avec une liberté de déplacement de cette dernière par rapport à la dite ceinture refroidie dans la direction axiale des cylindres, la ceinture refroidie étant supportée sur la dite platine, et la plaque en réfractaire isolant étant conformée de manière que l'effort de poussée transmis par la platine à la dite plaque soit retransmis par celle-ci uniquement à la dite plaque en matériau réfractaire dur.

With these objectives in view, the invention relates to a continuous casting device between cylinders of thin metallic products, comprising two cooled counter-rotating cylinders, two lateral closure walls and means for supporting and applying pressure to said walls shutter against the edges of the cylinders, said support means comprising:

• a thrust plate movable in the axial direction of the cylinders and arranged perpendicular to this direction,
• a plate, which supports the closure wall and which is carried by the thrust plate and disposed opposite it,
• at least three thrust members interposed between said thrust plate and said plate, these members being distributed over a region of shape corresponding to that of the closure wall, and being able to exert on it thrust forces independently l '' of one another, the plate being shaped so that the thrust force which it transmits is applied only to said wall, characterized in that, the closure wall consisting of a plate of refractory material hard surrounded by a metal belt to which it is linked, the said metal belt is fixed on a cooled belt surrounding a plate of heat-insulating refractory material, with a freedom of movement of the latter relative to the said cooled belt in the direction axial of the cylinders, the cooled belt being supported on said plate, and the insulating refractory plate being shaped so that the eff thrust ort transmitted by the plate to said plate is retransmitted by the latter only to said plate made of hard refractory material.

The plate is only supported by the plate thrust, that is to say that it is linked to it mechanically only in the vertical direction and possibly horizontally, perpendicular to cylinder axes. On the other hand, the plate can be move relative to the push plate on the one hand in the direction of the cylinder axes, and on the other hand by pivoting relative to it about an axis any located in the general plane of this plate, substantially orthogonal to said axial direction.

These different authorized movements are of course limited in amplitude, but sufficient to allow the shutter wall to apply as best as possible against the edges of the cylinders, even if the edges respective cylinders are not perfectly coplanar. In addition, when the closure wall is caused during casting to move away from the song of a cylinder, for example following the passage of a parasitic solidification of the metal poured between this cylinder and the shutter wall, the latter may slightly rotate on itself and therefore keep the best contact possible with the second cylinder, while without this freedom of movement, such parasitic solidification would push back the wall as a whole and create a clearance between it and the second cylinder.

Furthermore, during such a pivoting, the organs thrust located on the side where the closing wall deviates from the cylinder are more heavily stressed, and, in reaction, it is possible to act preferentially or only on these without significantly modifying the thrust on the side of the second cylinder.

The pushing members can be jacks piloted or springs.

In the case where the thrust members are cylinders, we can then control them individually either in pressure or in displacement, which allows apply a bigger push just where where such additional thrust is required, for example in the case indicated above, on the side where occurred parasitic solidification.

In the case where the thrust members are springs, this additional thrust is actually generated automatically by compression of the springs, on the side where the closure wall is spaced from the cylinders, and therefore by the increase in the force exerted by the compressed springs, since the position of the push plate is fixed.

Preferably, the stiffness of each spring and the distribution of the springs in the said zone are determined so that, for the same arrow of these springs, the pushing force they exert in the lower part of the obturation wall is greater than the thrust force exerted in the upper part of the wall. This provision allows for the fact that that the pressure exerted on the sealing wall by the cast metal is stronger at the bottom of this wall than towards the top, on the one hand because of the hydrostatic pressure liquid metal, on the other hand because of the effect of rolling by the cylinders on the current metal solidification, near the neck between the cylinders, which tends to widen the casting strip and therefore to push back the bottom of the cover wall. To get this particular distribution of the pushing force, we can play either on the stiffness of the springs, or on the positioning and distribution of springs in the plane of the thrust plate, which is more easily achievable when the number of springs is sufficient great, either on these two parameters at the same time.

In the case of the use of cylinders, the choice of the location of these will also take into account the desired distribution of enforcement efforts sealing wall on the cylinders. This choice is however less restrictive, since this distribution efforts can be made by piloting adequate cylinder pressure.

In addition to the advantage already indicated of being able to distribute according to a predetermined configuration the thrust exerted on the end wall 3 and not to move back the entire wall in the event of parasitic solidification, the invention also makes it possible to be able to modulate during the casting the overall bearing force, by moving the said thrust plate 10 relative to the cylinders, while retaining the adaptability of the position of the wall shutter in relation to the edges of the cylinders. AT To this end, the push plate is carried by a carriage mobile 8 in said axial direction, and the device includes means for moving said carriage by compared to the cylinders and exert on it an effort directed towards the cylinders. For example, by moving the push plate to cylinders, springs 14 all undergo additional compression, which is added to that which they had before this displacement, but which retains a similar distribution of thrust on the surface of wall 3, while accentuating more strongly the effort in the areas where the springs were already making a greater effort. So by example, the position of the push plate can be initially set at start-up to compress the springs quite strongly, thus ensuring a kind of lapping of the obturation wall against cylinder edges; then the overall downforce can be reduced, in stabilized pouring regime, to especially avoid too rapid wear of the wall shutter, and increased in the event of an incident, by example of liquid metal infiltration, to restore the sealing as quickly as possible.

Other characteristics and advantages will appear in the description which will be made of a device for continuous casting between cylinders of thin strips in steel.

• la figure l est une vue en coupe de l'ensemble de support de la paroi d'obturation latérale, dans le cas où les organes de poussée sont des ressorts,
• la figure 2 est une vue en coupe selon la ligne II - II de la figure 1, montrant la répartition des ressorts dans le plan de la paroi de poussée.
• la figure 3 est une vue partielle agrandie de la figure 2.

Reference is made to the appended drawings in which:

• FIG. 1 is a sectional view of the support assembly for the lateral closure wall, in the case where the thrust members are springs,
• Figure 2 is a sectional view along line II - II of Figure 1, showing the distribution of the springs in the plane of the thrust wall.
• FIG. 3 is a partial enlarged view of FIG. 2.

In the figures, the same elements are designated by identical references.

In the drawing of Figure 1, only one of the cylinders l of the casting installation, against the edge 2 from which the closure wall 3 is pushed, carried by a support assembly 4.

This support assembly includes a rigid frame 5, which carries a first carriage, or carriage prepositioning 6, adjustable in position on the chassis 5, in the axial direction A of the cylinders, for example by a screw-nut system 7.

The prepositioning carriage 6 carries a second carriage 8, guided in translation in the axial direction A. The position of the second carriage 8 is adjusted by a cylinder 9 for positioning and pushing.

The second carriage 8 supports a push plate 10, by means of two support pins 11. Furthermore, the push plate 10 is held against supports 12 linked to the carriage 8 and adjustable in position, so known per se, to ensure the verticality of the plate thrust 10.

The push plate 10 has a plurality of bores 13, distributed over a form area triangular corresponding to the shape of the wall shutter. In each bore 13 is placed a spring compression 14 supported by one end at the bottom of the bore, and by the other end on a piston 15 sliding in the bore and comprising means for retainer 16 to hold spring and piston in the bore.

The push plate 10 also has at its upper part of the support blocks 17, 17 ', on which rest ears 18, 18 'of a cooled plate 19 internally and the rear face of which is in contact with pistons 15.

One of the support blocks 17 has a rib 17B which engages with reduced play in a groove corresponding to the ear 18, to ensure the lateral positioning of the plate according to Ox (direction horizontal), while leaving it free to rotate according to Oz (vertical direction). The other 18 'ear rests simply on the support block 17 '. In short, the plans 17A and 17'A forming on the support blocks 17 and 17 ', the load-bearing surfaces, set the altitude according to Oz of the obturation wall, the rib 17B fixes the position according to Ox and the direction according to Oy is free. Means 20 of lateral stop of the lower end of the plate 19 relative to the support plate 10 are also provided to avoid tilting on the supports 17 and 17 '.

A plate 21 of insulating refractory material is held against the front face of the plate 19, by a cooled metal belt 22 which surrounds it and which is suspended on the plate by a hook-shaped pin 23, which rests in a cradle 24 of said plate, with some freedom of movement in the direction axial Oy. The insulating refractory plate 21 can also move relative to the cooled belt 22, in the axial direction, and has a thickness slightly higher than that of said belt 22.

On the cooled belt is screwed a second metal belt 25, surrounding the closure wall 3 which is linked to it by a refractory cement and whose the thickness is also greater than that of the said second belt 25, so as to protrude therefrom side of the cylinders, to avoid contact between them and the belt 25, even after maximum wear allowed.

The shapes and dimensions of the two plates refractories 3 and 21 and belts 22 and 25 are such that even when the second belt 25 is tightened on the cooled belt 22, the refractory plate insulator 21 is only in contact with the closure wall 3, and not with said second belt 25.

As also the thickness of the plate in insulating refractory 21 is greater than that of the belt cooled, the thrust force transmitted by the plate 19 is retransmitted only to the wall closure 3, and not on the belt 25, which avoids create constraints between this belt and the material shutter wall refractory, and therefore risks of deformations thereof or its separation from the belt 25.

When attaching the second belt 25 to belt cooled 22, there may be a displacement of the latter towards the cylinders; it is why the connection with the insulating refractory plate 21 is not rigid, and the hook 23 also has a some freedom of movement in the cradle 24, in the axial direction.

Preferably, the plate 19 is made of steel, of same as the cooled belt 22, and the second belt 25 is made of a material which has good hot characteristics such as steel or cast iron, its natural cooling being assisted by contact with the belt 22 cooled by a internal circulation of water.

Before the start of casting, it is necessary to preheat the closing wall 3. For this, the support assembly 4 is distant from the cylinders, the chassis 5 being for this purpose provided with means, known in self, not shown, to ensure its displacement relative to the structure of the installation of casting.

A radiation preheating oven is then brought in front of the shutter wall to carry it at a high temperature, the insulating refractory 21, the cooled plate 19 and the cooled belt 22 limiting the heating of the rest of the device.

Just before starting, the oven and evacuated, then the chassis 5 is brought back into position and clamped on the structure. The jack 9 is then controlled to bring the obturation wall in contact with the edges of the cylinders and continuing its movement, move the plate thrust 10, which has the effect of compressing the springs 14. The jack 9 is regulated in position. The effort he provides is transmitted to the push plate by the carriage 8 and its supports 12, and this effort is then distributed on the plate 19 by the springs; the efforts supplied locally by each of said springs 14 are so essentially a function of the compression of these and therefore the relative position of the plate and the push plate.

Thus, for a determined position of the jack 9, the closure wall 3 is applied against the cylinders 1 in a position that ensures the best contact possible. Indeed, even if, for example, the songs of two cylinders are slightly warped or offset axially with respect to each other, the wall shutter is applied against the two cylinders, with minimal play. However, the efforts of thrust, on the side of the cylinder whose edge overflows by compared to each other, are higher, which will lead to faster wear on this side of the sealing wall 3, and therefore tend to bring its general plan parallel to that of the push plate 10, lead to a more homogeneous distribution of the efforts provided by springs 14, and obtain optimal contact for the seal between obturation wall 3 and cylinders l.

During casting, if a solidification parasite appears between a cylinder and the wall shutter, this recedes on the side of said cylinder, but keep the best possible contact with the second cylinder. The said recoil compresses the springs on the side where it occurs and increases spontaneously as a result the pushing force on this side; it follows a increased friction which leads more or less quickly to the elimination of said solidification.

In the event of increased wear of a side of the closure wall, the springs 14 will act so that the closing wall remains in contact with the cylinder located on this side. This displacement can be detected either by a displacement sensor, either by a reduction of the pushing force, resulting because the springs located on the said side are thus less tablets. The jack 9 can then be controlled to advance the thrust plate towards the cylinders, until the desired effort is restored application of the sealing wall against the edge of the cylinder on the side where wear has occurred. In doing so, the efforts on the other side are increased and therefore go lead to accelerated wear on this other side, which will result in bringing back the sealing wall parallel to the thrust plate, and therefore regain optimal sealing.

Thus, the springs 14 not only allow absorb faults in the shutter wall contact - cylinder, but tend to provide correction automatic, spontaneous of these faults. Unlike the previous technique indicated above where one erodes continuous refractory wall to ensure the best possible contact with the cylinders, by pushing it against these with great effort, the invention allows on the one hand to reduce this pushing force, and on the other hand to use the obturation wall only when a contact disturbance occurs.

Additionally, even in the absence of such disturbances, the device according to the invention makes it possible to adjust the force of the shutter wall against the edge of the cylinders, in particular according to each stage of the casting, by a simple control of the jack 9. We can by example exert significant force when starting the casting, to perform a kind of lapping of the wall shutter against the edge of the cylinders, then reduce this force in stabilized pouring regime, and voluntarily increase it in the event of an incident, for example liquid metal infiltration.

In an alternative embodiment of the device already indicated, the springs can be replaced by piloted jacks which will perform the same functions as the springs, from the measurement of their internal pressure, and of the position of the closure wall. Each of the jacks can be individually regulated according to predefined laws, to ensure for example either a force proportional to the displacement, the jacks then acting as springs, or a constant force, or according to laws of the type F = Kx not or F = Ke x , where F is the force, K and n of the predefined constants, x the displacement of the rod of the jack, measured for example indirectly by sensors for displacement of the closing wall or of the plate.

In addition, a synchronization regulation of the wear of the closure wall, acting on all cylinders, can be combined with regulation individual, for example by defining one of the cylinders as a pilot and enslaving others on the cylinder pilot.

Preferably then, we will choose as cylinder pilot the one located towards the bottom of the obturation wall, that is to say near the neck between the cylinders, where the wear on the sealing wall is generally more accentuated.

Claims (6)

1. Device for continuous casting of thin metal products between rolls, including two cooled counter-rotatory rolls (1), two lateral closure walls (3) and means for supporting and applying by pressure the said closure walls against the edges (2) of the rolls, characterized in that the said support means include:

   a thrust plate (10) which can be moved in the axial direction (A) of the rolls (1) and is arranged perpendicular to this direction,

   a panel (19), which supports the closure wall (3) and which is carried by the thrust plate (10) and arranged facing the latter,

   at least three thrust members (14) interposed between the said thrust plate (10) and the said panel (9), these members being distributed over a zone of shape corresponding to that of the closure wall (3), and being capable of exerting thereon thrust forces independently of one another, the panel (19) being designed so that the thrust force which it transmits is applied only on the said wall (3), characterized in that, the closure wall consisting of a plate (3) of hard refractory material surrounded by a metal belt (25) to which it is connected, the said metal belt (25) is fixed on a cooled belt (22) surrounding a plate of thermally insulating refractory material (21), with freedom of displacement of the latter with respect to the said cooled belt (22) in the axial direction of the rolls, the cooled belt (22) being supported by the said panel (19), and the insulating refractory plate (21) being designed so that the thrust force transmitted by the panel to the said plate (21) is retransmitted by the latter only to the said plate of hard refractory material (3).
2. Device according to Claim 1, characterized in that the said thrust members are springs (14).
3. Device according to Claim 2, characterized in that the stiffness of each spring (14) and the distribution of the springs in the said zone are determined so that, for the same flexion of these springs, the thrust force which they exert in the lower part of the closure wall is greater than the thrust force exerted in the upper part of the wall.
4. Device according to Claim 1, characterized in that the thrust members are controlled jacks.
5. Device according to Claim 4, characterized in that the jacks are pressure-regulated.
6. Device according to one of Claims 1 to 5, characterized in that the thrust plate (10) is carried by a carriage (8) which can be moved in the said axial direction, and in that it includes means (9) for displacing the said carriage with respect to the rolls and for exerting thereon a force directed towards the rolls.

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