DE102017101777B4 - Bend-straightening machine and method for bend-straightening a metallic flat product - Google Patents

Abstract

Bending straightening machine for straightening a flat product (P) consisting of a metal material, the bend straightening machine (B) having a set of lower straightening rolls (1,3,5,7,9,11) and a set of upper straightening rolls (2,4,6, 8,10) and at least one drive (14 - 24) for driving the straightening rollers (1-11), the lower straightening rollers (1,3,5,7,9,11) and the upper straightening rollers (2,4, 6,8,10) are arranged along a conveyor path (12) extending between an input area (E) and an output area (A) of the straightening machine (B), which the flat product (P) to be straightened passes during straightening operation, and the upper and the lower straightening rollers (1-11) are offset in the conveying direction (F) of the flat product (P) and positioned opposite one another in such a way that the flat product (P) to be straightened in each case as it passes through the conveying path (12) presses the straightening rollers (1-11) each wraps around a portion of its circumference, characterized in that each of the lower straightening roll en (1,3,5,7,9,11) and each of the upper straightening rollers (2,4,6,8,10) is assigned a separate drive (14 - 24) that the speed and torque of the drives ( 14 - 24) can be adjusted separately for each of the straightening rollers (1 - 11), that at least one of the straightening rollers (1-6) assigned to the entry area (E) can be used as a braking roller and at least one of the straightening rollers (7 - 11 ) is designed as a pull roller and that s a control device (25) is provided, via which and the respectively assigned drive (14 - 24) each of the straightening rollers (1 - 11) is driven in use in such a way that the roller peripheral surface (28,29) , with which the straightening rollers (1 - 11) each sit on the facing surface (PO, PU) of the flat product (P) to be straightened, rotates at a peripheral speed (Vu) which is equal to the speed Vo of the respective straightening rollers (1 - 11) adjacent surface (PO, PU) of the flat product (P), at the same time the difference between the Ri Actual operation of the braking force (FB1 - FB6) applied by the respective brake roller (1 - 6) to the flat product (P) to be straightened and the tensile force (FZ7 - FZ11) applied by the respective pull roller (7 -11) to the flat product (P) to be straightened ) can be adjusted as a function of a target stretch by which the flat product (P) is to be permanently lengthened as it passes through the conveying path (12).

Description

The invention relates to a bend straightening machine for straightening a flat product made of a metal material, the bend straightening machine comprising a set of lower straightening rollers and a set of upper straightening rollers and at least one drive for driving the straightening rollers, the lower straightening rollers and the upper straightening rollers being arranged along a an input area and an output area of the bend-straightening machine, which the flat product to be straightened passes during straightening operation, and wherein the lower and upper straightening rollers are offset in the conveying direction of the flat product and positioned in relation to one another in such a way that the flat product to be straightened in each case as it passes through the Conveyor path wraps around the straightening rollers in each case by a portion of their circumference.

The invention also relates to a method for bend-straightening a metallic flat product using a bend-straightening machine configured in the manner specified above.

The flat products to be straightened with a machine according to the invention or with a method according to the invention are rolled products, such as strips, sheets or blanks and blanks obtained therefrom, the thickness of which is significantly less than their width and length. Typically, such flat products are produced by hot or cold rolling from a preliminary product, such as a slab, thin slab or cast strip, which consists of suitable steel or light metal materials.

Flat products produced in this way often have flatness or other geometric errors that are unavoidable due to the production process. These defects can be longitudinal strip curvature, also known as "strip camber" in the trade, and result from varying strip lengths across the strip width. Band saws can, for example, cause the band-shaped flat product to run sideways if the flat product to which the band saw is attached is to be conveyed as a band over a longer transport distance. Other strip irregularities, such as ripples or the like, can also impair the further processing of the flat product if the flat product is to be guided through processing machines provided for this purpose.

As for example in the EP 0 865 839 A2 explained, flatness defects in flat products of the type in question can be eliminated by so-called bend straightening. During bend straightening, the flat product to be straightened is guided under tension along several bending rollers. The bending rollers are offset from one another in such a way that the flat product, which is under tensile stress, is subjected to bending deformation at each bending roller. The bending direction changes from bending roll to bending roll. The straightening result is therefore dependent on the one hand on the bending radius or the respective angle of wrap on the straightening rollers and on the other hand on the tensile force exerted on the strip, ensuring a certain degree of stretching. Bending radius and tensile force are interrelated in stretch-bend straightening in that the bending radius decreases with increasing strength of the strip material while the tensile force remains the same. In order to ensure a sufficient bending radius, it is therefore necessary to increase the tensile force with increasing material strength and thickness of the flat product.

Furthermore, it is known that the flatness of metallic flat products can also be improved by so-called "stretch leveling". In this method, the flat product is clamped in sections between two collets, which are then moved apart in the longitudinal direction of the flat product, so that the flat product experiences a defined plastic stretch in the longitudinal direction (see http://redbudindustries.com/stretcher-levelers/). The disadvantage of this process is that it can only be carried out discontinuously and that the collet chucks leave marks on the surface of the sheet, which usually have to be cut out of the sheet (see manual "Forming", Carl Hanser Verlag, Munich, 2012 , p. 556, ISBN 978-446-42778-5).

Against the background of the prior art explained above, the task arose of creating a machine and a method with which the advantages of the methods known from the prior art for improving flatness can be used in combination.

With regard to the machine, the invention has achieved this object by means of a bend straightening machine having the features specified in claim 1.

With regard to the method, the solution to the above-mentioned object proposed by the invention consists in proceeding as specified in claim 10 during bend straightening.

Advantageous refinements of the invention are specified in the dependent claims and are explained in detail below, along with the general idea of the invention.

A bend straightening machine according to the invention for straightening a flat product consisting of a metal material therefore comprises, in accordance with the prior art mentioned at the outset, a set of upper straightening rollers and a set of lower straightening rollers as well as at least one drive for driving the straightening rollers. The upper straightening rollers and the lower straightening rollers are arranged along a conveying path which extends between an input area and an output area of the bend-levelling machine and which the flat product to be straightened passes during straightening operation. At the same time, the upper and lower straightening rollers are offset in the conveying direction of the flat product and positioned opposite one another in such a way that the flat product to be straightened wraps around the straightening rollers around a partial section of their circumference as it passes through the conveying path.

According to the invention, at least one of the straightening rollers assigned to the entry area is designed as a braking roller and at least one of the straightening rollers assigned to the exit area is designed as a pull roller in such a bend straightening machine. In addition, the difference between the braking force applied by the respective brake roller to the flat product to be straightened during straightening operation and the tensile force applied by the respective pull roller to the flat product to be straightened can be adjusted as a function of a target elongation by which the flat product is permanently lengthened as it passes through the conveyor path shall be.

A bend straightening machine according to the invention is thus set up in such a way that on the one hand, like a conventional bend straightener, it improves the flatness of the flat product to be straightened by repeated bending with the bending direction changing from straightening roller to straightening roller. In addition, however, a bend straightening machine according to the invention is also set up to subject the flat product passing through it in straightening operation to a tensile load which is so great that the flat product is permanently lengthened plastically. In a bend-straightening machine according to the invention, conventional straightening can thus be combined with stretch-straightening, which is also known per se, and although this stretch-straightening also aims at permanent lengthening of the flat product, the straightening process is not carried out discontinuously with the flat product being clamped in sections, but is carried out continuously .

In the method according to the invention for bend-straightening a metallic flat product using a bend-straightening machine, which comprises a set of upper straightening rollers and a set of lower straightening rollers and at least one drive for driving the straightening rollers, the upper straightening rollers and the lower straightening rollers extending along a line between an input area and a exit area of the bend-straightening machine, which the flat product to be straightened passes during straightening operation, and the upper and lower straightening rollers are arranged offset in the conveying direction of the flat product and infed against one another in such a way that the flat product to be straightened in each case hits the straightening rollers as it passes through the conveying path wraps around a section of its circumference, at least one of the straightening rollers assigned to the entry area of the bend straightener is used as a braking roller and at least one is assigned to the exit area of the bend straightener chine is operated as a pull roller, with the difference between the braking force applied by the respective brake roller to the flat product to be straightened during straightening operation and the tensile force applied by the respective pull roller to the flat product to be straightened being adjusted in such a way that the flat product passes through the conveyor path is permanently lengthened by a target stretching amount.

Typically, the change in length required for effective optimization of the flatness corresponds to an elongation of about 0.2-0.5% in the longitudinal direction of the flat product, which corresponds to the conveying direction through the bend-straightening machine.

In that a bend-leveling machine according to the invention has at least one straightening roller operated as a brake roller, which is assigned to the entry area of the machine and is therefore passed first by the flat product to be straightened, viewed in the conveying direction through the bend-levelling machine, and a straightening roller operated as a pull roller, which is assigned to the exit area of the machine and is accordingly arranged after the straightening roller operated as a braking roller, viewed in the conveying direction of the flat product, the tensile force acting on the flat product to be straightened and, associated with it, the permanent longitudinal elongation that is imposed on the flat product in the machine according to the invention can be precisely adjusted.

A major advantage of the procedure and design of a bend straightening machine according to the invention is that even with conventional bend straightening, the bending deformation of the flat product on the straightening rolls to the plastic range. The additional forces required for the permanent elongation, ie permanent plastic deformation of the flat product in the longitudinal direction, carried out according to the invention in the straightening machine, are then only comparably small. It has been found that the tensile forces required for this, which have to be applied in a bend-levelling machine according to the invention in addition to the tensile force required for conveying the flat product through the machine, only correspond to about one-fifth of the forces that are required in conventional, discontinuous stretch-levelling. to impose the desired elongation on the flat product.

The transmission of the braking forces to the flat product to be straightened can be optimized by designing at least one of the upper straightening rollers assigned to the entry area and at least one of the lower straightening rollers assigned to the entry area as a braking roller. By designing two or more upper or lower straightening rollers assigned to the entry area as braking rollers, the braking forces can be distributed more evenly over the straightening rollers in question, so that their wear and the load on the flat product to be straightened is reduced.

It can be equally advantageous if at least one of the upper straightening rollers assigned to the exit area and at least one of the lower straightening rollers assigned to the exit area is designed as a pull roller. Here, too, it can be expedient with a view to reducing wear and uniformly introducing the tensile forces into the flat product to be straightened if two or more upper or lower straightening rollers, which are assigned to the exit area, are designed as pulling rollers.

In principle, it is possible to provide further straightening rollers between the straightening rollers acting as braking rollers and as pulling rollers, on which the flat product to be straightened is only bent without additional braking or pulling forces being applied to the flat product. However, with regard to the desired defined elongation and the minimization of wear on the straightening rollers, it can be advantageous if the upper straightening rollers and the lower straightening rollers are each divided into an inlet-side group of straightening rollers, which are designed as braking rollers, assigned to the entry area and one group assigned to the exit area output-side group of straightening rollers are divided, which are designed as pull rollers, so that the flat product to be straightened experiences its plastic elongation along the conveying path between the input-side group and the output-side group of straightening rollers. In this configuration, the flat product to be straightened is exposed to the maximum tensile load between the two groups, so that the point at which the lengthening desired according to the invention occurs within the machine is known exactly. The control according to the invention of the straightening rollers acting as braking or pulling rollers is particularly simple and effective in this way.

Typically, the upper and lower straightening rollers are matched to one another in such a way that the number of lower straightening rollers is “1” greater than the number of upper straightening rollers and one upper straightening roller is assigned to one of the gusset spaces delimited by two adjacent lower straightening rollers. Conversely, the number of upper straightening rollers can be “1” greater than the number of lower straightening rollers and each upper straightening roller can be assigned to one of the gusset spaces delimited by two adjacent lower straightening rollers.

When we talk about “upper” and “lower” straightening rollers, this refers to an arrangement along a horizontally aligned conveying path. It goes without saying that the invention can be used in exactly the same way if the conveying path does not run exactly horizontally but rather at an angle in space or is aligned vertically. With these arrangements of the conveying path, too, the straightening rollers naturally retain their position above or below the conveying path.

Another embodiment of the invention that is important in practice is characterized in that each of the upper straightening rollers and each of the lower straightening rollers is assigned a separate drive. In principle, it is conceivable to drive the straightening rolls all together or in groups via a central drive in a bend straightening machine according to the invention, with a gear being arranged between the respective drive and the straightening rolls, via which the speed and the torque (braking effect/tractive effect/neutral) can be adjusted. However, since each individual straightening roller is assigned its own, individually controllable drive, the braking and tensile forces applied to the flat product to be straightened in a bend straightener according to the invention can be precisely metered in a particularly simple manner. This applies in particular when the speed and the drive torque can be set separately for each of the straightening rollers.

The roller wear and the load on the flat product to be straightened can be minimized by driving the upper straightening rollers and the lower straightening rollers separately from one another and by adjusting the speed of the straightening rollers in straightening operation in such a way that their peripheral speed is equal to the speed of the rollers that are in contact with them Surface portion of the flat product is.

A bend-straightening machine according to the invention is particularly suitable for straightening metal strips, in particular steel or light metal strips, with thicknesses of up to 20 mm.

• 1 eine Biegerichtmaschine in seitlicher Ansicht;
• 2 einen Ausschnitt X von 1 in vergrößerter Ansicht;
• 3 eine zweite Biegerichtmaschine in seitlicher Ansicht.

The invention is explained below with reference to a drawing showing an exemplary embodiment. They each show schematically:

• 1 a side view of a bend straightening machine;
• 2 a section X of 1 in enlarged view;
• 3 a second bend straightening machine in side view.

For the sake of clarity, only the components of the bend-straightening machine B that are necessary for understanding the invention are shown here.

Accordingly, the bend straightening machine B comprises a set of five upper straightening rolls 2,4,6,8,10 and a set of six lower straightening rolls 1,3,5,7,9,11. The lower straightening rollers 1,3,5,7,9,11 are arranged with axes of rotation aligned parallel to one another above a horizontally aligned conveyor path 12, via which the flat product P to be straightened in straightening operation from an input area E, where the flat product P into the bend straightener B is fed in, is conveyed in the conveying direction F through the bend-straightening machine B to an output region A, at which the flat product P emerges from the bend-straightening machine B.

The upper straightening rollers 2,4,6,8,10 are positioned parallel to the axis of the lower straightening rollers 1,3,5,7,9,11 below the conveying path 12 in a corresponding manner. The upper straightening rollers 2,4,6,8,10 are each offset in the conveying direction F in relation to the lower straightening rollers 1,3,5,7,9,11 so that an upper straightening roller 2,4,6,8, 10 is assigned in the gusset area 13, which is formed by two adjacent lower straightening rollers 1.3; 3.5; 5.7; 7.9; 9:11 is limited.

Each of the straightening rollers 1 - 11 is assigned its own individually adjustable rotary drive 14 - 24 and an actuating device, via which the straightening rollers 1 - 11 can be advanced in the vertical direction V in the direction of the conveying path 12 . This infeed takes place in a manner known per se such that the straightening rollers 1 - 11 dip into the conveying path 12 and as a result the flat product P to be straightened wraps around each of the straightening rollers 1 - 11 over a partial area of its circumference on its way through the bend straightening machine B. Accordingly, the flat product P is bent on the conveyance path 12 by the bend straightener B at each of the straightening rolls 1-11, with the bending direction changing from straightening roll to straightening roll 1-11.

In addition, the straightening rollers 1-11 can be associated in a manner known per se with supporting rollers or rollers, which are not shown here and which support the straightening rollers 1-11 against the loads that occur during the straightening operation.

The drives 14 - 24 are coupled to a control device 25 via which the speed and the drive power of each individual drive 14 - 24 can be set individually.

The straightening rollers 1-11 are divided into a group GB of straightening rollers 1-5 operated as braking rollers and a group GZ of straightening rollers 6-11 operated as pull rollers. Of course, it would also be conceivable to operate straightening rollers 1-5 as pull rollers and straightening rollers 6-11 as braking rollers.

The group GB includes the lower straightening rolls 1,3,5 and the upper straightening rolls 2,4,6, each located closer to the entry area E than the other straightening rolls 7-11 .

On the other hand, the group GZ comprises the upper straightening rollers 6, 8, 10 operated as pull rollers and the lower straightening rollers 7,9,11, which are positioned closer to the exit area A than the straightening rollers 7 - 11. As such, the straightening rollers 6 - 11 are the exit area assigned to A.

As a result of the bending taking place on the straightening rollers 1 - 11, the flat product P to be straightened has a greater speed on its outer surface PO, PU in relation to the respective straightening roller 1 - 11 than on its surface directly adjacent to the relevant straightening roller 1 - 11 other surface PU,PO.

During straightening operation, each of the straightening rollers 1 - 11 is driven via the control device 25 and the associated drives 14 - 24 in such a way that the circumferential surface 28, 29 of the roller, with which the straightening rollers 1 - 11 are each on the facing surface PO, PU of the flat product P seated, rotates at a peripheral speed Vu, which is equal to the speed Vo of the surface PO,PU of the flat product P in contact with the straightening rollers 1-11. In this way, in the area of contact, i.e. in the area in which there is contact between the flat product P to be straightened and the respective straightening roller 1 - 11, the relative speed between the circumferential roller surfaces 28, 29 and the rollers coming into contact with them Surface PO,PU equals "0" with the result that the abrasive wear on the straightening rollers 1 - 11 and the flat product P is minimized.

At the same time, the braking forces FB1 - FB6 applied via the leveling rollers 1 - 5 and the tensile forces FZ7 - FZ11 applied via the leveling rollers 6 - 11 are matched to one another in such a way that the flat product P to be leveled in the area of the transition 30 from the group GB of those operated as braking rollers Straightening rollers 1 -5 to the group GZ of straightening rollers 6 - 11 operated as pull rollers is permanently lengthened by an amount in the longitudinal direction of the flat product P, which coincides here with the conveying direction F, which corresponds to a plastic elongation of 0.2 - 0.3%.

When straightening the flat product P, about 80% of the cross section of the flat product P is brought into the plastic range. This reduces the cross section to be taken into account for permanent plastic elongation of the flat product P to 20% of the original cross section of the flat product P, with the result that only 20% of the tensile force required for conventional stretch straightening is required for the plastic length change sought according to the invention to stretch the flat product P section by section until a permanent plastic longitudinal elongation of 0.2 - 0.3% is reached. This achieves an effective improvement in the planarity of the flat product P compared to a pure bend-straightening treatment.

If the flat product to be straightened is, for example, a rolled strip material consisting of a high-strength steel material with a thickness d of 10 mm, a width b of 2000 mm and a yield point σz of 1000 N/mm ² , the result is for a plastic elongation with uniaxial load required tension Z to $$\text{Z}=\text{i.e}\times \text{b}\times \text{E}=10\text{mm}\times 2000\text{mm}\times 1000\text{N}/{\text{<figure-callout id="2" label="mm" filenames="DE102017101777B4\_0005.png" state="{{state}}">mm</figure-callout>}}^2=\mathrm{20,000}\text{KN}\text{.}$$

For the reasons explained above, the minimum tension Z′min required for a permanent elongation in a bend straightening machine B according to the invention is only 20% of the tension Z, ie in the example considered here $$\text{Z'min}=0.2\times \text{Z}=\mathrm{4,000}\text{CN}\text{.}$$

Accordingly, the straightening rollers 1 - 6 acting as brake rollers and the straightening rollers 7 - 11 acting as tension rollers are adjusted in the bend straightening machine B in such a way that the tension Z' acting on the flat product P in the area of the transition 30, which results from the difference in the in the area of the transition 30 effective braking forces FB applied by the straightening rollers 1 - 6 and tensile forces FZ applied by the straightening rollers 7 - 11 is determined by so much greater than the tension Z'min determined in the manner mentioned above that the desired permanent elongation of the flat product is achieved by 0.2 - 0.3%.

In the 3 illustrated variant of a straightening machine B', which is particularly suitable for practice, is in principle constructed in the same way as the straightening machine B, but has only three upper straightening rollers 2', 4', 6' and four lower straightening rollers 1', 3', 5''7' on.

This number of straightening rollers 1' - 7' are in the in 3 considered application is sufficient to apply the braking forces FB′ and tensile forces FZ′ required for the permanent elongation desired according to the invention to the steel strip P′ to be bend-straightened in the bend-straightening machine B′.

For this purpose, the upper straightening roller 2', which is located in the gusset area delimited by the lower straightening rollers 1',3', and the two lower straightening rollers 1',3' are combined into a group GB' and act as braking rollers, which Are assigned bend-straightening machine B 'and accordingly the steel strip P' on its way through the bend-straightening machine B 'passed first.

The upper straightening rollers 4′, 6′ and the lower straightening rollers 5′, 7′, on the other hand, are combined into a group GZ′ and act as pull rollers that are assigned to the output area A′ of the bend straightener B′.

The steel strip P' passing through the bend-straightening machine B' in the conveying direction F' from the entry area E' to the exit area A' is thus subjected in the area of the bending rollers 1' - 3' to a braking force FB' directed against the conveying direction F', whereas in the area of the bending rollers 4'-7' is subjected to a tensile force FZ'. As a result, the steel strip P' is permanently lengthened in the area of the transition between the group GB' and GZ'.

With the invention, a machine and a method are thus available with which optimized flatness of flat products P made of a metal material can be achieved by straightening the bends. The bend-levelling machine B according to the invention has lower straightening rollers 1,3,5,7,9,11 and upper straightening rollers 2,4,6,8,10 and at least one drive 14-24 for driving the straightening rollers 1-11. The straightening rollers 1 - 11 are arranged along a conveyor path 12 which extends between an entry area E and an exit area A of the bend straightener B, along which the flat product P to be straightened passes during straightening operation, and the upper and lower straightening rollers 1 - 11 are arranged in such a way that the flat product P to be straightened wraps around the straightening rollers 1-11 around a partial section of their circumference as it passes through the conveying path 12. According to the invention, at least one of the straightening rollers 1-6 assigned to the entry area E is designed as a braking roller and at least one of the straightening rollers 7 - 11 assigned to the exit area A is designed as a pulling roller, with the difference between the braking force applied by the braking roller 1 - 6 to the flat product P to be straightened FB1 - FB6 and the tensile force FZ7 - FZ11 applied by the pull roller 7 - 11 to the flat product P to be straightened can be adjusted as a function of a target elongation by which the flat product P is to be permanently lengthened as it passes through the conveying path 12.

Reference List

B, B'

bend straighteners

1, 3, 5, 7, 9, 11

lower straightening rolls

1', 3', 5', 7'

lower straightening rolls

2, 4, 6, 8, 10

upper straightening rolls

2', 4', 6'

upper straightening rolls

12

conveyor path

13

gusset area

14 - 24

rotary drives

25

control device

28, 29

roller peripheral surface

30

Transition between the group GB of straightening rollers 1 - 6 and the group GZ of straightening rollers 7 - 11

P, P'

flat products to be straightened (e.g. made of a metal material, in particular a steel material, rolled strip material)

A, A'

Output area of the respective bend straightening machine B, B'

E, E'

Entry area of the respective bend straightener E,E'

f

conveying direction

FB1 - FB6

braking forces

FB1' - FB3'

braking forces

FZ7 - FZ11

tensile forces

FZ4' - FZ7'

tensile forces

GB

Group of straightening rollers 1 - 6 operated as braking rollers

GB'

Group of straightening rollers 1' - 3' operated as braking rollers

GZ

Group of straightening rollers 7 - 11 operated as pull rollers

GZ'

Group of straightening rollers 4' - 7' operated as pull rollers

PO, PU

Surfaces of the flat product P

V

vertical direction

vu

Circumferential speed of the roll peripheral surface 28.29

Vo

Speed of the surface PO,PU of the flat product P in contact with the straightening rollers 1 - 11

Z'

tension acting on the flat product in the region of the transition 30

Claims (11)

Bending straightening machine for straightening a flat product (P) consisting of a metal material, the bend straightening machine (B) having a set of lower straightening rolls (1,3,5,7,9,11) and a set of upper straightening rolls (2,4,6, 8,10) and at least one drive (14 - 24) for driving the straightening rollers (1-11), the lower straightening rollers (1,3,5,7,9,11) and the upper straightening rollers (2,4, 6,8,10) are arranged along a conveyor path (12) extending between an input area (E) and an output area (A) of the straightening machine (B), which the flat product (P) to be straightened passes during straightening operation, and the upper and the lower straightening rollers (1-11) are offset in the conveying direction (F) of the flat product (P) and positioned opposite one another in such a way that the flat product (P) to be straightened in each case as it passes through the conveying path (12) presses the straightening rollers (1-11) each wraps around a portion of its circumference, characterized in that each of the lower guide whale zen (1,3,5,7,9,11) and each of the upper straightening rollers (2,4,6,8,10) is assigned a separate drive (14 - 24) that the speed and torque of the drives ( 14 - 24) can be adjusted separately for each of the straightening rollers (1 - 11), that at least one of the straightening rollers (1-6) assigned to the entry area (E) can be used as a braking roller and at least one of the straightening rollers (7 - 11 ) is designed as a pull roller and that s a control device (25) is provided, via which and the respectively assigned drive (14 - 24) each of the straightening rollers (1 - 11) is driven in use in such a way that the roller peripheral surface (28,29) , with which the straightening rollers (1 - 11) each sit on the facing surface (PO, PU) of the flat product (P) to be straightened, rotates at a peripheral speed (Vu) which is equal to the speed Vo of the respective straightening rollers (1 - 11) adjacent surface (PO,PU) of the flat product (P), where at the same time the difference between the R t operation of the braking force (FB1 - FB6) applied by the respective braking roller (1 - 6) to the flat product (P) to be straightened and the tensile force (FZ7 - FZ11) applied by the respective pulling roller (7 -11) to the flat product (P) to be straightened ) can be adjusted as a function of a target stretch by which the flat product (P) is to be permanently lengthened as it passes through the conveying path (12). bend straightening machine claim 1 , characterized in that at least one of the lower straightening rollers (1,3,5) assigned to the entry area (E) and at least one of the upper straightening rollers (2,4,6) assigned to the entry area (E) is designed as a braking roller. Bending straightening machine according to one of the preceding claims, characterized in that two or more lower or upper straightening rollers (1 - 6) assigned to the entry area (E) are designed as braking rollers. Bending straightening machine according to one of the preceding claims, characterized in that at least one of the lower straightening rollers (7, 9, 11) assigned to the exit area (A) and at least one of the upper straightening rollers (8, 10) assigned to the exit area (A) are designed as pull rollers is. Bending straightening machine according to one of the preceding claims, characterized in that two or more lower or upper straightening rollers (7 - 11), which are assigned to the exit area (A), are designed as pull rollers. Bending straightening machine according to one of the preceding claims, characterized in that the lower straightening rollers (1, 3, 5, 7, 9, 11) and the upper straightening rollers (2, 4, 6, 8, 10) are each located in one of the entry areas (E) assigned input-side group (GB) of straightening rollers (1-6), which are designed as braking rollers, and the output area (A) assigned output-side group (GZ) of straightening rollers (7 - 11), which are designed as pull rollers, see above that the flat product (P) to be straightened undergoes its plastic elongation along the conveying path (12) between the group (GB) on the inlet side and the group (GZ) on the outlet side of straightening rollers (1-11). Bending straightening machine according to one of the preceding claims, characterized in that the number of lower straightening rolls (1,3,5,7,9,11) is "1" greater than the number of upper straightening rolls (2,4,6,8, 10) and a respective lower straightening roller (2,4,6,8,10) is assigned to one of the gusset spaces (13) delimited by two adjacent upper straightening rollers (1,3,5,7,9,11). Bending machine according to one of Claims 1 until 6 , characterized in that the number of upper straightening rollers is “1” greater than the number of lower straightening rollers and one lower straightening roller is assigned to one of the gusset spaces delimited by two adjacent lower straightening rollers. Bending straightening machine according to one of the preceding claims, characterized in that the speed and the drive torque can be adjusted separately for each of the straightening rollers (1 - 11). Method for straightening a metal flat product (P) by means of a straightening machine (B) comprising a set of lower straightening rolls (1,3,5,7,9,11) and a set of upper straightening rolls (2,4,6,8, 10) and at least one drive (14 - 24) for driving the straightening rollers (1 - 11), the lower straightening rollers (1,3,5,7,9,11) and the upper straightening rollers (2,4,6, 8,10) are arranged along a conveyor path (12) extending between an entry area (E) and an exit area (A) of the straightening machine (B), which the flat product (P) to be straightened passes during straightening operation, and the lower and upper Straightening rollers (1 - 11) are offset in the conveying direction (F) of the flat product (P) and positioned opposite one another in such a way that the flat product (P) to be straightened in each case moves the straightening rollers (1 - 11) by wraps around a section of its circumference, characterized in that at least one of the input area (E) d he straightening roller (1 - 6) assigned to the straightening machine (B) is operated as a braking roller and at least one straightening roller (7 - 11) assigned to the output area (A) of the straightening machine (B) is operated as a pulling roller and that the difference between the in straightening operation of the respective braking roller (1 - 6) the braking force (FB) applied to the flat product (P) to be straightened and the tensile force (FZ) applied by the respective draw roller (7 - 11) to the flat product (P) to be straightened is adjusted in such a way that the flat product ( P) is permanently lengthened during its passage through the conveying path (12) by a desired stretching amount and that the lower straightening rollers (1,3,5,7,9,11) and the upper straightening rollers (2,4,6,8,10) are separated are driven by each other and in straightening operation the speed of the straightening rollers (1 - 11) is set in such a way that their peripheral speed (Vu) is equal to the speed (Vo) of the surface section (PO, PU) of the flat product (P) that is in contact with them. procedure after claim 10 , characterized in that a first group (GB) assigned to the entry area (E) is formed by lower and upper straightening rollers (1-6) which are operated together as braking rollers, and a second group (GZ) assigned to the exit area (A) is formed by lower and upper straightening rollers (7 - 11), which are operated together as drawing rollers.

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