EP0730918B1 - Method and device for levelling flat metal products, such as metal bands, sheet metal - Google Patents

Abstract

A process is claimed for planishing flat metal products (30) such as plates, sheets or strip. The product is passed between two assemblies of planishing rollers (5,51,53). The rollers (51) of one assembly being staggered in the direction of defilement (F) with respect to the rollers (53) of the other assembly. The two assemblies are spaced and positioned in such a manner that the product is subjected to a series of alternate flexions of decreasing amplitude. Compensation is made for the strain of the rollers provoked by the stresses imposed by the product on the rollers. This compensation is applied independently for each roller, in a manner that ensures that all the longitudinal fibres of the product are subjected to the series of bending deformations for which the amplitudes and the variations of the amplitude in the direction of defilement are essentially identical over the width of the product. The device used to put this process into service is also claimed.

Description

The present invention relates to a method and a device for leveling flat products such as strips, metal sheets or sheets, especially of steel, that one will designate thereafter generally under the name of sheet metal, according to the preamble of claims 1 and 3.

Document FR-A-2 334 440 describes a process according to the preamble of claim 1 with the exception of the characteristic relating to the use of adjustable yield compensation means independently from one roll to another.

Leveling devices, called levelers, are used in order to remove flatness defects sheets after hot or cold rolling. Indeed, for example after the hot rolling phases (in a cage reversible quarto for sheets or in the finishing train for bands), cooling and packaging, laminated products may have non-developable flatness defects, such as defects called long edges or long center, or developable flatness defects, such as defects hanger or tile. These geometric defects affect visibly the rolled products.

On the other hand, it happens that a sheet apparently plane deforms when it is later cut, by releasing internal constraints which were subject the blank area before cutting. More precisely, these defects result from a heterogeneity of the constraints internal in the sheet, both in the direction longitudinal than in the direction transverse to the rolling direction.

The aim of the planing operation is to remove these defects, developable and non-developable, and ensure stability of the sheet after cutting, by removing or at least minimizing constraints internal.

The principle of leveling by a leveler of the type concerned with the invention is to submit the sheet in scrolling through a succession of alternating flexions, including the amplitude decreases gradually at the end of the operation. In roller levelers, this succession of bending is ensured during the passage of the sheet between leveling rollers staggered and being nested into each other so as to cause said alternating bending, this nesting reducing, in the direction of movement of the sheet, to produce the so-called progressive decrease in amplitude inflections.

The strong bends to which the sheet is subjected at the entry of the leveler are required to allow sufficiently laminate the material to remove basically the initial geometry faults not developable. Insofar as the deformations of alternating bending, combined with the pulling effect caused by the sheet metal drive, are sufficiently important, there is plasticization of all fibers of material over the entire width of the sheet. But these large deformations generally create a distribution non-homogeneous internal longitudinal stresses (leading to the defect called hanger) and transverse (defect called tile) in the thickness of the sheet. In effect, although there is plasticization of the whole material, this plasticization is more or less important according to the initial geometry faults. To ensure correct leveling, this distribution heterogeneous constraints must be removed, and the intensity of the constraints must be reduced, in a next phase, which is practically achieved by the succession of flexions of decreasing amplitude towards the exit from the dresser.

A leveling is really effective when the sheet obtained is perfectly flat before cutting, and the rest after any cutting, which can only result of a gradient of residual internal stresses after the lowest possible leveling. Only a deformation homogeneous sheet over its width provides these lowest residual stress gradients possible.

The levelers currently known (see for example document DE-A-3 308 616 which corresponds to the preamble of claim 3) feature generally, in addition to conventional means for adjusting position of the leveling rollers located on both sides of the sheet metal trajectory, yielding compensation, or counter-bending systems, adjustable to prevent bending of the rollers gliders under the effect of the efforts to which they are submitted during planing. So, for example, in the Figure 1 which schematically represents a leveler for thin sheets, support rollers 9 are placed on a support frame 7 and held in contact with the leveling rollers 5. These are thus supported by the so-called support pebbles, which limit the flexural deformations of the rollers. We note that the glider rollers are fitted swiveling in bearings (not shown in the Figure 1) linked to a frame 3 of each box spring of the leveler (upper bed base 1, lower bed base 2). At minus one of these bases, being adjustable in position, adjusts the spacing of the two sets of rollers gliders 5, while, in each box spring, the rollers of support 9 are linked to the support frame 7, which makes it same part of the box spring, and can only be more or less pressed against the leveling rollers to avoid the deformations of these. A typical system of counter-bending adjustment consists of a set of bias wedges 11 placed between the bed base and the chassis of the support rollers; the relative horizontal displacement of said bias wedges, controlled by a motor 13, leads to press more or less strongly all of the rollers support 9 against the leveling rollers 5 and thus limit the deformation of the latter under the effort of bending of the sheet. Other means of adjusting the against bending, such as cylinders, are also known and used to act on the support rollers to ensure offset compensation on all glider rollers a box spring, upper or lower, or both box springs.

However, it has been found that these leveling often did not allow for flatness sufficient, the sheets coming out of the leveler having again either flatness defects visible at the exit of the leveler, such as long edges or long center, either defects revealed only during cutting, such as that hanger or saber faults, the latter being a defect resulting in a deformation of curvature of the sheet in his own plan.

The present invention aims to solve the problems mentioned above and aims in particular to allow the manufacture and supply of sheets with the smallest flatness defects possible, especially less than 3 mm / m, and do not presenting no risk of occurrence of such defects after delivery to the user, when the latter proceeds to their cutting.

With these objectives in view, the object of the invention is a leveling process for flat metal products such as as sheets, sheets or strips with the features of claim 1.

Thanks to the process according to the invention, it is possible to ensure an efficient and effective leveling, which ensures the sheet production not only free from defects flatness geometry at the exit of the leveler, but also having an internal stress gradient very low practically eliminating the risks appearance of flatness defects later, when of the implementation of the sheet by cutting.

In fact, the inventors discovered, as a result in-depth studies of the leveling process carried out in levelers according to the prior art, that the flatness defects that may remain after the operation leveling results in particular from deformation rate different between the different longitudinal fibers of the produced during successive alternate bending to which it is subjected by the leveling rollers. These differences in treatment of the material of the sheet metal across its width cause even when the product seems to plane out of glider, large gradients transverse internal constraints, which manifest themselves later, for example after cutting the sheet, by deformations of the blanks from the sheet, strip or planed sheet.

The inventors sought the possible causes of these heterogeneities in the treatment of sheet metal during the leveling carried out according to prior techniques. A first cause appeared in existence, in sheet metal laminated before planing, fiber defects, of the type "long edges" or "long center". These faults are not developable, are in principle corrected during first alternate bending performed by the first rollers of the leveler, which must lead to plastic deformations of the material. Due to faults of aforementioned fibers, these deformations do not produce however not the same effect on all fibers, the longest fibers being less plasticized than the shorter fibers, and this results in the appearance of internal stress gradients already mentioned. The alternately flexion of amplitude gradually decreasing then applied to the product by the Glider rollers located downstream are in principle intended to homogenize the state of internal stresses and reduce their intensity.

Tests carried out by the inventors on levelers classically used today have shown that this homogenization was not effective, that the effects of bending strain conditions, variables in the width of the sheet, suffered by it at the entry of the leveler had repercussions downstream and even in exit from the leveler, and that even if the first inflections led to some transverse homogeneity of the distribution of constraints, this homogeneity was not found in exit from leveler.

These tests consisted in particular in passing in a leveler currently used in industry steel sheets on both sides of which were placed strain gauges on the one hand in the center and on the other hand near the shores, and to follow the deformations thus measured during the scrolling of the sheet metal. Two plots representing these measurements are shown as an example in Figures 3 and 4. These plots relate to thin sheets (a few mm), but strictly similar results have been obtained for thicker products or thin leaves.

In these figures, the curves J1, J5 and J2, J6 correspond to the deformations measured in µm / m by the gauges placed towards the banks, and the curves J3, J4 correspond to the deformations measured by the gauges located in the center of the sheet. Each peak 21, 23 of different curves corresponds to the passage of the area of sheet fitted with gauges on a leveling roller (respectively 51, 53), as shown diagrammatically in Figure 2, the difference in abscissa between peaks successive corresponding to the distance between the planes vertical axes of two successive rollers. The pics directed downwards correspond to the gauges located on the face of the sheet in contact with the leveling roller concerned, subjected to compression deformation, and the peaks directed upwards correspond to the gauges located on the other side, subject to elongation.

These curves therefore visualize the evolution of deformations throughout the leveler shown schematically figure 2.

The plots in Figure 3 were obtained with a minimal compensation for roller yielding, performed by the means of compensation for ceding equipping levelers commonly used to date, from type of those shown in Figure 1, i.e. acting simultaneously on all the rollers of a box spring by an identical displacement of the supports of the rollers of support of each roller.

It can be seen that with such compensation of weak yielding, the deformations measured at the edge (curves J1, J5 and J2, J6) are almost twice as much larger than those measured in the center (curves J3, J4), and this over the entire length of the leveler. The inventors thus found that a relationship existed between on the one hand the difference in deformations undergone by the central fibers and by the fibers near the banks and, on the other hand, the flatness defects of the sheet metal at the exit from the leveler. This difference of deformation could be explained by the fact that, following insufficient transfer compensation, every rollers flexed under the bending forces of the sheet metal, the air gap between the rollers then being more important in their middle part only towards the edges, and leading to the observed deformation, weaker in the central zone of the sheet metal only towards the banks.

• l'apparition de défauts de type bords longs sur des tôles minces, dés la sortie de la planeuse, même en absence de tels défauts avant planage, ceci pouvant s'expliquer par une déformation plastique des bords plus importante que celle subie par le centre, du fait que l'entrefer au centre était plus important que l'entrefer sur les bords;
• des déformations de la tôle lors de découpes ultérieures (cintre variant lors de la découpe, défaut de sabre apparaissant lors du refendage), dues à un gradient transversal de contraintes non nul (contraintes de compression orientées dans le plan de la tôle sur les bords de celle-ci, résultant de l'aplatissement des bords dont la longueur était, après la plastification provoquée par les premiers rouleaux, supérieure à celle du centre, lui même moins déformé ; et contraintes de traction réciproques dan le centre),
• une persistance des défauts de type bords longs ou centre long
     et donc globalement à une dégradation de la planéité initiale.

Such leveling conditions have led to:

• the appearance of defects of the long edge type on thin sheets, as soon as they exit the leveler, even in the absence of such defects before planing, this can be explained by a plastic deformation of the edges greater than that undergone by the center, the fact that the air gap in the center was more important than the air gap on the edges;
• deformations of the sheet during subsequent cuts (hanger varying during cutting, defect of saber appearing during slitting), due to a non-zero transverse stress gradient (compression stresses oriented in the plane of the sheet on the edges of this, resulting from the flattening of the edges, the length of which was, after the plasticization caused by the first rollers, greater than that of the center, itself less deformed; and reciprocal tensile stresses in the center),
• persistence of long edge or long center type defects
  and therefore overall to a degradation of the initial flatness.

Other tests were then carried out by overcompensating yielding, to avoid bending of rollers, especially at the entry of leveler, and so remove long edge type faults. It is resulted in an over-deformation of the center of the sheet by compared to the edges, generating deformations on cutting (hanger and / or saber), and the appearance of type defects long center for thin sheets.

In yet other trials, the results of which are illustrated in FIG. 4, the ceding compensation has been adapted until we can see that deformations caused by the first rollers were roughly equivalent across the width of prison. In the various tests thus carried out, he was found that flatness defects remained in exit of the leveler, and that correlatively, the deformations measured at the rollers located in downstream towards the exit of the leveler, were clearly larger in the center of the sheet (curves J'3, J'4) only towards the banks (curves J'1, J'5 and J'2, J'6).

Based on these various test results, and noting that it was not possible to carry out a satisfactory leveling by known methods of setting work of the levelers currently used, the inventors then imagined the process according to the invention, as defined above. Indeed, in compensating for yielding individually on each roll, it is possible to control the deformations generated by each roller in the different zones the product, by adapting the Authorized bending of the roll or counter bending exercised on it by means of compensation for ceding, in particular taking into account to settle this offset compensation, efforts that each roll supports specifically.

In comparison, the known leveling methods involved a ceding compensation setting identical for all rollers; gold like efforts suffered by the rollers located downstream are less than those suffered by the input rollers due to the least deformations imposed on the product, their own yielding is also less. And like, in the levelers according to prior art, the yield compensation is identical, in terms of displacement of the support rollers, for all the rollers, this results in either significant yielding, and so excessive deflection, input rollers, in the case of optimal compensation on the rollers output, i.e. excessive counter-bending of the rollers output, in the case of optimal compensation on the input rollers.

In these two cases, the air gap between two rollers successive (a lower roller and an upper roller) cannot be kept constant over their length for all the rollers, which necessarily leads to different product deformations in its different longitudinal zones, and therefore the existence of a gradient transverse of constraints unacceptable to flatness required. Contrary to this, the process according to the invention makes it possible to adjust the yield compensation for each roll, and therefore ensures the air gap optimal for each pair of rollers, whatever its position in the leveler, and therefore to submit the produced at substantially identical deformations on all its width.

It will be noted however that these bending deformations identical across the width of the product are not necessarily over the entire length of the leveler. Indeed, it may be necessary to adapt the transfer compensation applied to the very first roller (s) depending on the presence or not of edge type defects long or long center in the product to be leveled, so to subject the product during bending deformations to sufficient internal plasticization to remove or at least reduce these fiber defects first, before continuing with planing to reduce the intensity of internal constraints and to homogenize their distribution.

It is clear indeed that the output rollers, i.e. those located furthest downstream in the direction of sheet metal scrolling, must not undergo bending deformation, and therefore that their own yielding should be fully compensated as much as possible, for that the air gap between two successive rollers is the even over the entire width, so that the deformations of bending undergone by all the fibers of the sheet, on all its width, are identical on the last rollers located before the exit of the leveler.

By cons, this perfect constancy of the air gap over the entire width is not necessarily required, or even it may be desired that the air gap is not constant, for the input rollers, in order to adapt the deformations of the different fibers according to their state at the entry of the leveler. That is why, in accordance with the invention, the yielding of these rollers input need not be exactly compensated, but on the contrary adapted according to sheet metal defects before planing.

Therefore, it therefore appears necessary to ability to offset ceding individually on each roller. In addition, to ensure homogeneity transverse constraints across the width of the sheet, it would be desirable that the succession of deformation undergone by each fiber over the entire length of the leveler is identical for all fibers, in other words, that the history of the deformations is the even at all points across the width of the sheet. Now, from fact that, as indicated above, the deformations in output are actually identical, but the input distortions are not necessarily it is necessary to be able to also regulate the assignment of intermediate rollers, independently for each roller, to tend to what the so-called historical distortions are as similar as possible, fault to be able to be exactly identical. What comes back in made to ensure a compromise between conditions of yield compensation setting leading to curves in Figure 3 and ideal setting conditions in which the curves corresponding to the edges and center of the sheet would be confused over the entire length of the leveler, as they should be less in output.

The invention also relates to a device for leveling of flat metal products, allowing the setting using the method described above, this device being defined in claim 3.

According to one embodiment, the means of offset compensation include support rollers so-called gliding rollers, pressure means for apply the said rollers to the said rollers, and adjustment means, independent for each roller, of the pressure exerted by said rollers on the rollers.

Preferably, several sets of rollers are distributed along the length of each roll, each of these assemblies having means for adjusting the independent pressure.

• la figure 1 est une vue générale schématique d'une planeuse de tôle mince selon l'art antérieur,
• la figure 2 est une vue à plus grande échelle, montrant la disposition relative de quelques rouleaux planeurs et les déformations que subit la tôle lors du planage,
• la figure 3 est un graphique montrant les déformations, mesurées en µm/m, d'une tôle en cours de planage, lors de son défilement, dans une planeuse de l'art antérieur, avec une compensation de cédage minimale,
• la figure 4 est un graphique similaire, dans le cas d'une compensation de cédage réglée pour être optimale à l'endroit des déformations maximales de la tôle,
• la figure 5 est une vue de principe, en coupe transversale, du sommier supérieur d'une planeuse conforme à un mode de réalisation l'invention,
• la figure 6 est une vue partielle en coupe, selon la ligne VI - VI de la figure 5.

Other preferred characteristics and advantages will appear in the description which will be given of a leveler in accordance with an embodiment of the invention. Reference is made to the appended drawings in which:

• FIG. 1 is a general schematic view of a thin sheet leveler according to the prior art,
• FIG. 2 is a view on a larger scale, showing the relative arrangement of a few leveling rollers and the deformations which the sheet undergoes during leveling,
• FIG. 3 is a graph showing the deformations, measured in μm / m, of a sheet during planing, when it travels, in a leveler of the prior art, with minimal yield compensation,
• FIG. 4 is a similar graph, in the case of a yield compensation adjusted to be optimal at the location of the maximum deformations of the sheet,
• FIG. 5 is a principle view, in cross section, of the upper base of a leveler according to an embodiment of the invention,
• FIG. 6 is a partial sectional view, along the line VI - VI of FIG. 5.

We will not return to the drawings of Figures 1 to 4 which have already been described and commented on in the section introductory to this thesis and in the explanations previously reported on problems caused by sheet metal deformations, when these deformations are not homogeneous in its width.

We will only note, in relation to Figure 2 which illustrates the general principle of planing, the decrease in the amplitude of bending deformations sheet 30, in the direction of travel (arrow F), this decrease being caused by a separation increasing, in the direction of scrolling, of the two series of leveling rollers carried respectively by the base upper (series of rollers such as 51) and the box spring lower (series of rollers such as 53).

Figures 5 and 6 illustrate a mode of realization of the leveler according to the invention. Only the upper box spring 1 has been shown, the box spring lower being carried out in a similar manner.

The planer rollers 51 are mounted in rotation in bearings 61 linked to the frame 63 of the bed base.

Each roll is provided with compensation means ceding, consisting of several sets 65 of rollers support, distributed along the length of the rollers. The number of these sets depends on the length of rollers. Preferably, a set of rollers of support is located in the middle of the roller, and another together towards each of its ends. Others roller assemblies can be placed in positions intermediate when the rollers are long, for the leveling of sheets or large sheets.

Each set includes two support rollers 67 whose axes are offset on either side of the plane vertical passing through the axis of the roller 51, so as to support this one in the vertical direction, and also to prevent displacement or bending in a plane horizontal.Each pair of rollers 67 is mounted on a support 69, guided vertically in translation on the box spring 1.

A jack 71 is placed between the box spring and each support 69 of rollers, for pressing said rollers 67 against roller 51.

Although only five gliding rollers are shown in the drawing of Figure 6, it will be understood easily that this number can be larger.

Conventionally, all the rollers are mounted on a same bed base, and the adjustment of the spacing between the upper rollers and the lower rollers is performed simultaneously for all rollers by adjusting the relative position of the lower bed bases and upper, in spacing and tilting, i.e. in relative inclination so that the air gap between the lower and upper rollers are more important towards the exit of the leveler than towards the entry.

Preferably, the first roller (s) in entry leveler can however be adjusted in position independently of the rollers located downstream, so as to allow adjustment of the amplitude of the first bending deformations, without influencing that of the following rollers. For this purpose, for example, the upper input roller 52, can be mounted on a bed base 1 ', independent of bed base 1 supporting the exit glider rollers, and having its own means adjusting the distance between the roller 52 and the corresponding rollers of the lower base.

In addition, this first roller 52 is provided with means very powerful ceding compensation in order to correct flatness defects by selective stretching fibers (center or strands), the following rolls ensuring a progressive and homogeneous relaxation in the width of the sheet, made possible by the yield compensation individually adjustable on each roll.

The adjustment of the cylinders, and therefore of the counter-bending leveling rollers and determined according to characteristics of the product to be leveled, either by calculation, either by tests during which the forces undergone by the leveling rollers and from which we deduce the counter-flexions to be applied to each roller at by means of cylinders, or other similar actuators, acting on the support rollers. This setting is not normally not changed during the operation of leveling, although it is still possible to act at any time on any of the cylinders.

The leveler is provided with means for continuously measuring the forces exerted by the product on the rollers or the position of said support rollers or rollers, and means for control of the cylinders according to the measured forces or said measured positions, to adjust during leveling the counter-flexions on each roller.

The invention is not limited to the device for leveling which has just been described only as example. The number of rollers, the number of rollers per roller and the relative arrangement of the rollers in relation rollers may be changed without departing from the scope of the invention as claimed. Likewise, the means for adjusting the counter-bending described above can be replaced by other equivalent means known to those skilled in the art.

Similarly, these means of adjusting the pressure may be common to several sets of support rollers if you wish to reduce the cost of comes back from the machine. For example a single cylinder in middle position according to the generatrix of a roller and associated with a metal support plate interposed between the jack and the supports 69 may be suitable in this goal. In this case, however, as we understand, the possibilities for fine adjustment of the counter-flexions are correspondingly smaller, but may be sufficient to some facilities.

According to these wishes or necessities, the man of trade will thus be able to choose between a solution with means fully independent counter-bending by roller support, or pair of rollers 67, and a solution to means against bending common to several sets of rollers acting on the same glider roller 51, or even, along of the leveler, on successive leveling rollers

Claims (7)

1. Process for planishing flat metal products (30), such as plate, sheet or strip, in which the said product is made to run between two sets of planishing rolls (5, 51, 53), the planishing rolls (51) of one set being offset, in the running direction (F), with respect to those (53) of the other set, and the two sets being spaced apart and positioned so as to subject the product to a succession of alternating bending operations of decreasing amplitude, each of the said planishing rolls being provided with its own yielding-compensation means (67, 69) which are independently adjustable from one roller to another, so as to be able to compensate for the yielding of the planishing rolls which is caused by the forces exerted by the product on the said rolls, characterized in that the yielding of the rolls located downstream, towards the exit of the planishing mill, is compensated for in an independent manner for each roll in order to keep the gap between two successive rolls constant over the entire length of the said product so as to subject all its longitudinal fibres to successions of bending deformations whose amplitudes, and the amplitude variations in the running direction, are substantially identical over its entire width.
2. Process according to Claim 1, characterized in that the yielding on the first roll or rolls located upstream, in the direction in which the said product runs, is furthermore compensated for so as to subject it, during the bending deformations, to plasticization sufficient to eliminate the fibre defects without these deformations necessarily being identical over the width of the product.
3. Apparatus for planishing flat metal products, comprising at least one set of two beams (1, 2) each provided with a set of planishing rolls (5, 51, 53) each provided with its own yielding-compensation means (67, 69) independently adjustable from one roll to another, which apparatus is characterized in that it comprises at least two sets of beams (1, 1'), each of these sets having individual means for adjusting the distance between the beams, and in that it includes means for measuring the forces exerted by the product (30) on the rolls (51, 53) and means for controlling the said yielding-compensation means according to the forces measured.
4. Apparatus according to Claim 3, characterized in that the yielding-compensation means comprise support rollers (67) for the said planishing rolls and pressure means (69) for applying the said rollers to the said rolls and in that, for each roll, independent means (71) for adjusting the pressure exerted by the said rollers on the rolls (51) are provided.
5. Apparatus according to Claim 4, characterized in that several sets (65) of rollers (67) are distributed over the length of each roll, each of these sets having independent means for adjusting the pressure.
6. Apparatus according to Claim 4, characterized in that the means (71) for adjusting the pressure exerted by the said rollers on the rolls (51) are common to several sets (65) of rollers distributed over the length of each roll.
7. Apparatus according to Claim 4, characterized in that the means (71) for adjusting the pressure exerted by the said rollers on the rolls (51) are common to several sets (65) of rollers acting on successive rolls.

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