EP0560662B1 - Method and installation for rolling a metal plate - Google Patents

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.

Generally, 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 the passage of the product to be laminated. 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 laminated, 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 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.

The latter being thicker before passing through the cage, the support plane defined by the rollers of the table placed upstream should normally be placed below the upper generatrix of the lower working cylinder, and at a distance substantially equal to half the thickness reduction, 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 generator 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 as a result, the front end of the laminated plate can fall back on the output rollers and risk being damaged.

It has therefore been proposed, in a particular arrangement described in document JP-A-3,035,805 (, the closest prior art), to reinforce the anterior end of the slab by giving it a wavy shape.

To this end, the roller table constituting the feeding device placed on each side of the cage is associated with a pair of spaced apart rollers disposed immediately upstream of the cage and between which the slab passes, these two rollers being able to be lifted or lowered simultaneously.

When engaging the slab, the two rollers are raised to determine an upward curvature of the head of the slab, and then lowered to form a downward curvature. We then return to the normal rolling position, the end of the slab being reinforced by the two inverted curvatures thus produced.

It follows, however, that the movable rollers, as well as the lifting and lowering means 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 as 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 was found that, after a few passes, the plate during rolling took a slightly curved shape and, therefore, only supported, in practice, on the table, 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 method of introducing a plate into a rolling mill making it possible, with reduction of equal thickness, to reduce the risk of refusal of engagement or, conversely, to increase the reduction of possible thickness at each pass.

The method according to the invention is defined by claim 1.

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, this is raised relative to 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 whose 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.

The installation according to the invention is defined by claim 5.

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 driven in rotation 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 movable frame 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, about an axis parallel to the axes of the working rolls and rests on an elastic lifting means by its side facing the cage.

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 schematically shows 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 a roller table improved 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 $\text{R = E - e}$

.

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 so as to define a horizontal plane 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 roller tables 3, 3 'serve 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 thickness reduction R so that the median plane Q, c ' 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 effort 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 provided 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 constituted by a number of rollers 41 closest to the cage 10, for example four rollers, which are mounted on a mobile chassis 42 vertically displaceable, 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 effort thrust 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 FIG. 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 being, 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 -This 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 we can also slightly raise the movable table 4 so that, in its position support intermediate of the front end 22, the contact plane P3 tangent to the upper generators of the rollers 44, 45, is shifted downward relative to the level of the upper generatrix 12 'of the lower cylinder 1' only by one distance h which can be adjusted between 0 and R / 2, R being the thickness reduction displayed for the pass considered.

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 determining 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 comes to be 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 drive roller, the last roller 45 of the table. In this case, the pushing 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 carried out differently.

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 which 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 to enter a metal slab (2) into a roll stand (10) comprising two working cylinders (1,1') separated by a roll gap (13) for the passage of the slab (2) and pressing means for the cylinders in order to roll the slab, and associated with at least a roller feeding device (3) located on at least one side of the roll stand (10) and comprising a plurality of feeding rollers with parallel axes, each feeding device comprising a fixed part (3) having a roller assembly (31) mounted onto a frame (33) and defining a supporting plane P1 for the slab (2) and a mobile part (4) having at least a last roller (45) located immediately upstream the roll stand (10) in the engagement direction and mounted onto a vertically mobile frame (4) and associated with lifting means (43) of said last roller (45) until a level higher than the supporting plane P1 of the fixed part (3), at least some of said feeding rollers being rotary driven in the direction of motion of the slab (2) towards the roll stand (10), in order to push it, by a friction effect towards the roll gap (13), characterized in that the lifting means of the mobile part (4) of the feeding device are resilient supporting means (43) which are tared in order to compensate the proper weight of the mobile part (4) added with the weight of the front end (22) of the slab (2) and in that the last roller (45) of the mobile part (4) is rotary driven in the engagement direction of the slab (2) so that without slab (2), the mobile part (4) is lifted by the resilient supporting means (43) until a high position provided by stops, above the supporting plane P1 and when the slab (2) rolling onto the fixed part (3) runs onto the mobile part (4) said latter is pushed back towards the bottom by the slab (2) until an intermediate position provided by the taring of the resilient supporting means (43) and for which at least said latter roller (45) is held perfectly applied against the inner face (20) of the slab (2) by said resilient supporting means (43) and thus provides onto the slab (2) a thrust load which is added to the load exerted at least by the first driven roller (32) of the fixed part (3) in order to enhance entering of the slab (2) into the roll gap (13).
2. Method to enter a slab (2) according to claim 1, characterized in that the resilient supporting means (43) are tared such as when the mobile part (4) supports only the weight of the front end (22) of the slab (2), said latter is first into contact with the upper cylinder (1) by means of the upper edge thereof (24) and following the moving thereof, is lowered by the upper cylinder (1) until it comes into contact with the cylinder (1') while pushing the mobile part (4) which yields elastically and whose application on the lower face (20) of the slab (2) is thus increased.
3. Method according to one of claims 1 and 2, characterized in that the roll gap (13) between the working cylinders being adjusted in order to determine a reduction (R) of the initial thickness E of the slab (2) down to a thickness (e), the resilient supporting means (43) of the mobile part (4) are tared so that when the latter supports the weight of the front end (22) of the slab (2), the median plane (Q) of the slab is substantially at the level of the median plane (P) of the roll gap (13).
4. Method according to one of claims 1 and 2, characterized in that, the roll gap (13) between the working cylinders being adjusted in order to determine a reduction (R) of the initial thickness E of the slab (2) down to a thickness (e), the resilient supporting means (43) of the mobile part (4) are tared so that when the latter supports the weight of the front end (22) of the slab (2), the median plane (Q) of the slab is slightly offset upwards with respect to the median plane (P) of the roll gap (13) so that, when moving towards the roll stand, the front end (22) of the slab (2) first comes into contact, by its upper edge (24) with the upper working cylinder (1) which determines the lowering of the slab (2) with at least the last roller (45) while increasing the application load of the former on the lower face (20) of the slab (2) until the slab has penetrated the roll gap (13).
5. Rolling unit of a metal slab (2) comprising a roll stand (10) having two working cylinders (1,1') separated by a roll gap (13) for the passage of the slab (2) and pressing means for the cylinders in order to roll the slab, and associated with at least a feeding device located on at least one side of the roll stand (10) and comprising a plurality of feeding rollers with parallel axes, each feeding device comprising a fixed part (3) having a roller assembly (31) mounted onto a frame (33) and defining a supporting plane P1 for the slab (2) and a mobile part (4) having at least a last roller (45) located immediately upstream the roll stand (10) in the engagement direction and mounted onto a vertically mobile frame (4) and associated with lifting means (43) of said last roller (45) until a level higher than the supporting plane P1 of the fixed part (3), at least some of said feeding rollers being rotary driven in the direction of motion of the slab (2) towards the roll stand (10), in order to push it, by a friction effect towards the roll gap (13), characterized in that at least the last roller (45) of the mobile part (4) is rotary driven in the engagement direction of the slab (2) and in that the mobile part (4) of the feeding device rests on resilient supporting means (43) providing without the presence of slab (2) a lifting means at least for the said last roller (45) until a high position provided by stops, above the supporting plane P1 of the fixed part, said resilient supporting means (43) being tared in order to compensate the proper weight of the mobile part (4) added with the weight of the front end (22) of the slab (2) such that when the slab (2) rolling onto the fixed part (3) runs onto the mobile part (4), said latter is pushed back towards the bottom by the slab (2) until an intermediate position provided by the taring of the resilient supporting means (43) and for which at least said latter roller (45) is held perfectly applied against the lower face (20) of the slab (2) and provides a further thrust means of the slab (2), said supporting means (43) allowing the mobile part (4) to be lowered by yielding elastically under a load exerted downwards by the slab (2) when entering the roll gap (13).
6. Rolling unit according to claim 5, characterized in that the mobile part (4) comprises a single roller (45) mounted onto a mobile frame (42) resting onto resilient supporting means (43) (54).
7. Rolling unit according to claim 6, characterized in that the mobile part (4) comprises a frame (42) carrying a plurality of rollers (41) in order to build a mobile table, whereas at least one (45) of said rollers (41) is rotary driven.
8. Rolling unit according to one of claims 5, 6 and 7 characterized in that at least a mobile roller (45) is rotary-driven in a synchronous manner with the driving rollers of the fixed part (3) by a common control means whose power is distributed automatically over the driving rollers coming into contact with the slab (2).
9. Rolling unit according to claim 7, characterized in that the set of rollers (41) (44) (45) of the mobile table (4) is rotary-driven in a synchronous manner with the driving rollers of the fixed part (3) by a common control means whose power is distributed automatically over the driving rollers coming into contact with the slab (2).
10. Rolling unit according to claim 6, characterized in that the frame (42) of the mobile table (4) rests entirely on resilient supporting means (43) to allow vertical motion while adapting to the orientation of the part (22) of the slab (2) which thus rests, during engagement at least on the two extreme rollers (44) (45) of the mobile table (4), whereas at least the extreme rollers (44) (45) are rotary-driven.
11. Rolling unit according to one of claims 6 and 7, characterized in that the mobile frame (42) is articulated, on its side (46) facing the roll stand, around an axis parallel to the axes of the working cylinders and rests on a resilient lifting means (54) by its side (47) directed towards the roll stand (10).

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