EP0560662A1 - Method and installation for rolling a metal plate - Google Patents

Abstract

The subject of the invention is a method for introducing a metal plate (2) into a rolling housing (cage, stand) (10) and an improved installation for facilitating the engagement of the plate in the nip (gap) (13) between the work rolls (1, 11) of the rolling mill. According to the invention, at least one of the latter rollers (45) of the table (3), placed immediately upstream of the housing (cage, stand) (10), in the direction of engagement, is mounted so as to be movable vertically with respect to the table (3) and is subjected to a lifting force which is at least equal to the weight of the front end (22) of the plate (2) so that, at the end of its advance towards the housing (cage, stand), the said front end (22) is supported by the movable roller (45) which is thus perfectly applied on the lower face (20) of the plate and is, moreover, driven in rotation in the direction of engagement so as to exert on the plate (2) a thrust force which is added to the force exerted at least by the first driven roller (32) of the table (3) in order to favour the introduction of the plate (2) into the nip (gap) (13). <IMAGE>

Description

The invention relates to a method for promoting the engagement of a metal plate in a rolling stand and also covers an installation for laminating metal plates improved so as to facilitate the engagement of the plates according to the method.

In general, a rolling mill cage comprises a set of rollers superimposed inside a rigid frame. For example, in a "Quarto" assembly, the rolling mill comprises two working rolls associated, respectively, with two support rolls and whose generators facing each other define an air gap for passage of the product to be la.miner. Clamping means, bearing on the rigid frame, determine a crushing action of the product whose thickness, at the entrance to the rolling mill, is greater than the air gap.

The product to be rolled, which has the shape of a bar or a flat plate, is normally brought to the cage by an input roller table comprising a plurality of rollers with parallel axes which define a plane of plate support placed substantially at the air gap. At least some of these rollers are rotated so as to cause, by friction, the advancement of the plate towards the working rolls. A second roller table, placed on the outlet side, receives the product after rolling.

In the so-called "reversible" rolling mills, the rolling stand is associated with two roller tables placed on either side and serving alternately as feeding table and receiving table depending on the direction of passage of the product.

As the latter is thicker before passing through the cage, the support plane defined by the rollers of the table placed upstream must normally be placed below the upper generator of the lower working cylinder, and at a substantially equal distance. to half the reduction in thickness, so that the horizontal median plane of the plate substantially coincides with the median plane of the air gap placed at equal distance from the two cylinders.

On the other hand, the support plane defined by the rollers of the output table should, theoretically, be placed at the level of the upper generatrix of the lower working cylinder, to receive the rolled product at its exit from the air gap. To avoid the risks of blockage, it is preferable to lower the output table slightly relative to the lower cylinder, but it follows that the anterior end of the laminated plate may fall back on the output rollers and risk being damaged.

It has therefore been proposed, in a particular arrangement described in document JP-A-30.35805, to reinforce the anterior end of the slab by giving it a wavy shape. For this purpose, the last roller is lifted from the input table above the normal level, by means of hydraulic cylinders bearing on two support chocks at the ends of the roller. There is thus produced, when the plate is introduced into the air gap, an upward curvature of its upstream end, which then takes a downward curvature, when the plate is properly engaged. We then lower the last roller to normal level to complete the pass.

It follows, however, that the movable roller and its chocks must withstand significant forces to cause the two curvatures of the plate. In addition, the front end of the plate must be curved to pass into the air gap, which makes engagement more difficult.

However, in general, the engagement of the plate in the air gap can present difficulties which lead to achieving a reduction in thickness smaller than that which would be allowed, theoretically, by the power of the rolling mill.

Indeed, when the product is already engaged between the working rolls, the crushing action exerted by the latter determines sufficient friction to cause the advancement of the product.

On the other hand, during the phase of entry into the cage, if a substantial reduction in thickness is to be achieved, the friction exerted by the cylinders on the edges of the plate may be insufficient to entrain the product and it it may be necessary to push on it to help it engage between the cylinders.

To promote the engagement of the plate, it can be given a certain speed before it comes into contact with the cylinders, so. to benefit from an inertia effect, but such an effect remains limited. There is therefore quite often a refusal of engagement which may require a reduction in the reduction in thickness compared to the desired value and allowed by the power of the rolling mill. The number of passes is thus increased.

To remedy this drawback, it is not sufficient to increase the torque applied to the driven rollers because the thrust force exerted on the plate depends on the friction between the latter and the rollers.

However, by studying the conditions of passage of the plate in the air gap, it has been observed that, after a few passes, the plate during rolling takes on a slightly curved shape and, therefore, does not, in practice, rest on the table, only by its edge opposite the cage, the pushing action often being exerted only by a single roller.

The object of the invention is to remedy this drawback by ensuring better application of the plate to be laminated to the table and, consequently, an increase in the thrust force exerted on the plate by the rollers.

The subject of the invention is therefore an improved process for introducing a plate into a rolling mill making it possible, with equal thickness reduction, to dimi reduce the risk of refusal of entry or, conversely, increase the reduction in thickness possible with each pass.

According to the invention, at least one of the last rollers of the table, placed immediately upstream of the cage, in the direction of engagement, is mounted movable, vertically, relative to the table, and is subjected to a lifting effort at least equal to the weight of the front end of the plate so that, at the end of its advancement towards the cage, said front end is supported by the movable roller which is thus perfectly applied to the underside of the plate and is also driven in rotation in the direction of engagement so as to exert on the plate a thrust force which is added to the force exerted at least by the first driven roller of the table to favor the introduction of the plate in the air gap.

To increase the pushing effect of said movable roller, it is advantageous to adjust the level of the latter so that, when it simply supports the weight of the anterior end of the plate, the latter is lifted relative in the median plane of the air gap and comes into contact, first, with the upper cylinder by its upper edge and, continuing its advancement, is lowered by the upper cylinder until contact with the lower cylinder by pushing the movable roller which yields elastically and the application force on the underside of the plate is thus increased.

The invention also covers an improved installation for implementing the method and generally comprising a rolling stand associated with at least one roller table, at least some of which are rotated in the direction of movement towards the cage of the plate to push it towards the air gap between the two working cylinders, respectively upper and lower.

According to the invention, at least one of the last rollers of the table, placed immediately upstream of the cage is rotated in the direction of engagement of the plate and is mounted vertically movable on the table by resting on the latter by means of at least one elastic lifting and applying means of said roller on the underside of the plate, said elastic lifting means being adjusted so as to substantially compensate for the weight of the anterior end of the plate increased by the own weight of at least said last roller and to allow the lowering thereof by yielding elastically under the effect of a downward action exerted by the plate during its introduction into the air gap.

Preferably, the last rollers of the support table closest to the cage are mounted on a frame resting on elastic lifting means and constituting a movable table, at least some of said rollers being rotated in the direction of engagement .

In a particularly advantageous manner, the driving rollers of the movable table and of the main table are driven in rotation in synchronism by a common control means, the power of which is distributed automatically over the rollers which are in constant contact with the plate.

In a first embodiment, the mobile chassis rests entirely on elastic support means, so as to be able to move vertically, adapting to the orientation of the part of the plate which rests on it.

In another embodiment, the mobile chassis is articulated, on its side opposite to the cage, around an axis parallel to the axes of the working rolls and rests on an elastic lifting means by its side facing the cage.

• La Figure 1 représente très schématiquement une cage de laminage réversible de type connu, dans un montage Quarto.
• La Figure 2 représente schématiquement une table à rouleaux perfectionnée selon l'invention.
• La Figure 3 représente l'installation dans la phase d'approche de la plaque 2 et la Figure 4 montre, à échelle agrandie, le début d'engagement d'une plaque 2.
• La Figure 5 représente plus en détail un mode de réalisation particulier d'une table à rouleaux perfectionnée selon l'invention, dans sa position relevée.
• La Figure 6 représente la table à rouleaux de la Figure 5 dans sa position abaissée.

However, the invention will be better understood from the following description of a particular embodiment given by way of example and shown in the accompanying drawings.

• Figure 1 very schematically shows a reversible rolling stand of known type, in a Quarto assembly.
• Figure 2 shows schematically an improved roller table according to the invention.
• Figure 3 shows the installation in the approach phase of plate 2 and Figure 4 shows, on an enlarged scale, the start of engagement of a plate 2.
• Figure 5 shows in more detail a particular embodiment of an improved roller table according to the invention, in its raised position.
• Figure 6 shows the roller table of Figure 5 in its lowered position.

In Figure 1, there is shown a rolling stand of the conventional type comprising, in a Quarto assembly, two working rolls 1, 1 ', bearing, respectively, on two support rolls 11, 11', and associated with two roller tables 3, 3 ', disposed respectively on either side of the clamping plane S in which the axes of the cylinders are placed and which is generally vertical.

The generators facing 12, 12 ′, of the two working rolls 1, 1 ′, are separated by an air gap 13 in which the product to be laminated is passed which is in the form of a plate 2.

The relative positions of the cylinders can be adjusted by means of clamping devices not shown in the Figure and, in practice, the width (e) of the air gap 13 is less than the thickness (E) of the product 4 so as to determine , during the passage of the product, a reduction in thickness R = E - e.

To determine the progress and the passage of the product 2, the rolling stand is associated with an input table 3 consisting of a series of rollers 31 with axes parallel to the axes of the working rolls 1, 1 ', and which are aligned to define a hori plane zontal P1 tangent to the rollers 31.

A second roller table 3 'is generally placed on the side of the outlet to receive the rolled product. In reversible rolling mills, the two 3.3 'roller tables are used alternately for entry and exit.

Normally, the support plane P1 of the input table 3 passes below the level of the upper generator 12 'of the lower working cylinder 1', at a distance substantially equal to half the reduction in thickness R of so that the median plane Q, that is to say the plane placed at equal distance from the two faces of the plate, coincides with the median plane P of the air gap.

The support plane P2 of the output table 3 ′ is placed substantially at the level of the upper generator 12 ′ of the lower working cylinder 1 ′ to receive the laminated product, a small difference in level being simply made to avoid the risks of blockage. .

As indicated, at least some of the rollers 31 of each roller table 3 (3 ') are rotated by means not shown so as to control the movement of the plate 2 towards the cage and its engagement between the cylinders 1, 1 '.

As long as the plate 2 is flat, it is supported almost regularly on the rollers 31 and the thrust force can be distributed among several driving rollers.

However, it has been observed that, after a few passes, the plate 2 could curve slightly, generally taking a convex shape upwards, as shown exaggeratedly in FIG. 1.

As a result, in practice, when the plate 2 is engaged between the rollers 1 and 1 ', the plate 2 is supported only by its edge 21 opposite the cage 10 on the roller 32 furthest from the cage and that the latter must exert the pushing force alone. As this force is transmitted only by friction, it may not be sufficient to cause the engagement of the front end 22 of the plate 2 between the rollers, thus causing a refusal of engagement if the reduction in thickness planned is too high.

The invention overcomes these drawbacks thanks to the arrangements shown schematically in Figures 2 and 3.

We see, in fact, in Figure 2, that the roller table 3 has been divided into several parts, a first part 33 produced in a conventional manner and comprising a set of rollers 31 mounted on a fixed frame, and a second part 4 consisting of a number of rollers 41 closest to the cage 10, for example four rollers, which are mounted on a movable frame 42 vertically movable, for example under the action of elastic support members 43.

In the absence of the plate 2, the movable frame 4 is raised by the support members 43 to a high position determined by stops not shown.

When the plate 2 rolling on the first part 3 of the table passes over the rollers 41 of the movable table 4, the latter is lowered to an intermediate position, determined by the support members 43 which are calibrated so as to compensate for the self-weight of the movable table 4 plus the weight of the front end 22 of the plate 2.

As indicated in Figure 3, the frame 42 can advantageously be supported entirely by elastic members 43 and it therefore takes the orientation corresponding to that of the plate 2 which is thus perfectly applied to all of the rollers 41 of the movable table by resting at least on the two end rollers 44, 45. The thrust force is thus distributed at least on three rollers, respectively the rear roller 32 and the two rollers 44, 45, of the movable table. It is therefore possible to exert on the plate 2 a greater thrust force which promotes the engagement of its front end 22 between the working rolls 1, 1 '.

It should be noted that the bending of the plate 2 has been exaggerated in Figure 3 and can, in practice, be reduced enough for the plate to be applied not only on the end rollers 44, 45, but also on the intermediate rollers 41 of the movable table 4 which must therefore also be rotated. In a particularly advantageous manner, all the driving rollers of the table 3 and of the movable table 4 are driven in rotation in synchronism by a common control means, the power of which is distributed automatically over the rollers which are, at a determined instant, in contact of the plate. Such a control means, easy to imagine, has not been shown in the Figures.

In the arrangement shown in Figure 3, the general level of the table 3 and the calibration of the springs 43 are determined so that, when the movable table 4 supports the plate 2, the median plane Q of the front end 22 of that -It is located substantially at the median plane P of the air gap 13, the two front edges 23, 24, coming into contact with the two cylinders 1, 1 ', roughly simultaneously.

The engagement of the plate is then carried out in excellent conditions, the friction effect of the cylinders 1,1 ', adding to the thrust forces F1, F2, F3, applied by the rollers 32, 44, 45 .

But it is also possible to slightly raise the movable table 4 so that, in its intermediate position for supporting the front end 22, the contact plane P3 tangent to the upper generatrices of the rollers 44, 45, is not shifted downwards with respect to at the upper generator 12 ′ of the lower cylinder 1 ′ only by a distance h which can be adjusted between 0 and R / 2, R being the reduction in thickness affi checked for the pass in question.

In this arrangement shown in Figure 4, the median plane Q of the plate 2 is then offset upward relative to the horizontal median plane P of the air gap 13 and the front end 22 comes into contact first with the cylinder upper working 1 by its upper edge 24 before meeting the lower cylinder 1 '.

Continuing its advancement, the plate 2 is lowered by the upper cylinder 1 by pushing down the movable table 4, which increases the adhesion with the rollers 44,45, until the lower edge 23 of the front end 22 in turn comes into contact with the lower cylinder 1 '. Thanks to the thrust force exerted by the two parts 3 and 4 of the roller table, it is exerted between the edges 23, 24, of the plate 2 and the working rolls 1, 1 ', sufficient friction for determine the engagement of the front end 22 between the cylinders 1,1 '.

It will be noted that the elastic mounting of the movable table 4 also makes it possible to reduce the forces which can be applied thereto by the rear end 25 at the end of the passage of the plate 2 when the latter is not perfectly rectilinear .

Of course, the invention is not limited to the details of the only embodiment which has just been described, and may be subject to variants remaining within the protective framework defined by the claims.

In particular, it is preferable to use a movable table 4 with several rollers and entirely supported by elastic means to allow it to be applied perfectly on the underside 20 of the plate. However, in a simplified embodiment, one could use a single movable driving roller, normally the last roller 45 of the table. In this case, the thrust force would still be distributed over at least two rollers, respectively the first roller 32 and the last roller 45 of table 3.

Furthermore, the elastic mounting of the movable table 4, which only has to move between two high and low positions, could be achieved in a different way.

For example, in the embodiment shown in Figures 5 and 6, the rear end 46 of the movable frame 42 is articulated on a fixed support 5 around a horizontal axis 51 while its front end 47 facing the cage 10 is supported on the end of a lever 52, by means of a connecting rod 53, the lever 52 being pivotally mounted about a horizontal axis on the fixed support 5 and its other end being articulated on a retaining member elastic, for example a spring or a jack, which determines the lifting of the front end of the table 4 in the raised position of Figure 5 and allows the lowering of the table 4 in the position of Figure 6, the retaining member 54 can be calibrated so as to adjust the level of the front roller 45 when the table 4, loaded by the front end 22 of the plate 2, is in its intermediate position.

The reference signs, inserted after the technical characteristics mentioned in the claims, have the sole purpose of facilitating the understanding of the latter and in no way limit their scope.

Claims (11)

1. Method for introducing a metal plate (2) into a rolling stand (10) comprising two working rolls (1, 1 ') separated by an air gap (13) for passage of the plate (2) and cylinder clamping means for rolling the plate, and associated with at least one roller table (3) placed on at least one side of the cage (10) and comprising a plurality of rollers (3) with parallel axes defining a plane P1 for supporting the plate (2), at least some of said rollers (3) being rotated in the direction of movement of the plate (2) towards the cage (10), so as to push the latter, by friction, towards the air gap (13),
characterized in that at least one of the last rollers (45) of the table (3), placed immediately upstream of the cage (10), in the direction of engagement, is mounted movable, vertically, with respect to at the table (3), and is subjected to a lifting force at least equal to the weight of the front end (22) of the plate (2) so that, at the end of its advancement towards the cage, said anterior end (22) is supported by the movable roller (45) which is thus perfectly applied to the underside (20) of the plate and is, moreover, rotated in the direction of engagement so as to exert on the plate (2) a thrust force which is added to the force exerted at least by the first driven roller (32) of the table (3) to promote the introduction of the plate (2) into the air gap (13) . 2. A method of introducing a plate (2) according to claim 1, characterized in that the level is adjusted, at least of the last support roller (45) so that, when the latter simply supports the weight of the front end (22) of the plate (2), this comes into contact, first, with the upper cylinder (1) by its upper edge (24) and, while continuing its advancement, is lowered by the upper cylinder (1) until contact with the lower cylinder (1 ') by pushing the movable roller (45) which yields elastically and whose application on the underside (20) of the plate (2) is thus increased. 3. Rolling installation of a metal plate (2) comprising a rolling stand (10) comprising two working rolls (1, 1 separated by an air gap (13) for passing the plate (2) and means for clamping the rolls for rolling the plate, and at least one roller table (3) placed on at least one side of the cage (10) and comprising a plurality of rollers (3) with parallel axes defining a plane P1 for supporting the plate (2), at least some of said rollers (3) being rotated in the direction of movement of the plate (2) towards the cage (10), so as to push the latter, by friction, towards the air gap (13), characterized in that at least one (45) of the last rollers of the table (3), placed immediately upstream of the cage (10) is rotated in the direction of engagement of the plate and is mounted vertically movable on the table (3) by resting on it by means of at least one elastic means (43) (54) for lifting and applying said roller (45) on the underside (20) of the plate (2), said elastic lifting means (43) (54) being adjusted so as to substantially compensate for the weight of the front end (22) of the plate (2) increased by the self-weight of at least said last roller (45) and to allow the lowering thereof by yielding elastically under the effect of a downward action exerted by the plate (2) during its introduction into the air gap (13). 4. Laminating installation according to claim 3, characterized in that at least the last roller (45) of the table (3) closest to the cage (10) is mounted on a movable frame (45) supported on the table (3) by means of at least one elastic means (43) (54). 5. Laminating installation according to claim 4, characterized in that the frame (45) carries a plurality of rollers (41) so as to form a movable table (4) constituting the last part of the table (3) most close to the shell (10), at least one (45) of said rollers (41) being rotated. 6. Laminating installation according to one of claims 3, 4 and 5, characterized in that at least the movable roller (45) is rotated in synchronism with the driving rollers of the table (3) by means common control whose power is automatically distributed on the drive rollers which are in contact with the plate (2). 7. Laminating installation according to claim 5, characterized in that the set of rollers (41) (44) (45) of the movable table (4) is rotated in synchronism with the driving rollers of the table ( 3) by a common control means, the power of which is automatically distributed over the drive rollers which are in contact with the plate (2). 8. Laminating installation according to claim 5, characterized in that the frame (42) of the movable table (4) rests entirely on elastic support means (43), so as to be able to move vertically by adapting the orientation of the part (22) of the plate (2) which thus rests, at the time of engagement, at least on the two end rollers (44) (45) of the movable table (4), at least said end rollers (44) (45) being rotated. 9. Laminating installation according to one of claims 4 and 5, characterized in that the movable frame (42) is articulated, on its side (46) opposite the cage, around an axis parallel to the axes of the cylinders of work and is supported on an elastic lifting means (54) by its side (47) facing the cage (10). 10. Laminating installation according to one of claims 3 to 9, characterized in that, the air gap (13) between the working rolls being adjusted so as to determine a reduction (R) of the initial thickness (E ) of the plate (2) to a thickness (e), the position of at least the movable roller (45) is adjusted so that, when the latter supports the weight of the front end (22) of the plate (2), the median plane (Q) thereof is located substantially at the median plane (P) of the air gap (13). 11. Laminating installation according to one of claims 3 to 9, characterized in that, the air gap (13) between the working rolls being adjusted so as to determine a reduction (R) of the initial thickness (E ) of the plate (2) to a thickness (e), the position of at least the movable roller (45) is adjusted so that, when the latter supports the weight of the front end (22) of the plate (2), the median plane (Q) thereof is slightly offset upward relative to the median plane (P) of the air gap (13) so that, advancing towards the cage, the end front (22) of the plate (2) first makes contact, by its upper edge (24), with the upper working cylinder (1) which then determines the lowering of the plate (2) with at least the roller mobile (45) by increasing the application force thereof on the underside (20) of the plate (2) until the engagement of the latter in the air gap (13).

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