Rolling device and rolling method using the rolling device

Abstract

The present invention relates to an apparatus for rolling, in particular step rolling, a rolled material, the apparatus comprising at least one pair of rolls, at least one linear actuator arranged downstream of the pair of rolls in the rolling direction and capable of applying a tensile stress to the rolled material together with the pair of rolls, and means for detecting the tensile stress. To enable an improved method for flexibly rolling a rolled material, the rolling apparatus is characterized in that it also comprises means for detecting the tensile stress and a control device for controlling the drive force of the linear actuator in relation to the detected tensile stress in order to selectively vary the tensile stress applied to the rolled material or to keep the tensile stress constant even when the drive speed downstream of the roll gap changes. The present invention also relates to a method for rolling the rolled material using such an apparatus.

Description

[Technical Field]

[0001] The present invention relates to an apparatus for rolling, in particular step rolling, a material to be rolled, the apparatus comprising at least one pair of rolls, at least one linear actuator arranged downstream of the pair of rolls in the rolling direction and capable of applying a tensile stress to the material to be rolled together with the pair of rolls, and means for detecting the tensile stress. The present invention also relates to a method for rolling a material to be rolled using such an apparatus. [Background technology]

[0002] Equipment for rolling and straightening metal strips is used in rolling, straightening and processing lines for metal strips. Metal strips are rolled and straightened for different purposes. In rolling, the strip is rolled to become thinner by being deformed by horizontal forces. In straightening, the strip is straightened by tension. Especially in stretch straightening, an attempt is made to minimize the area of ​​the strip under tension. The smaller the deformation area, the better the balance of the microstructure.

[0003] A special form of rolling is step rolling, also called "flexible rolling." It is used, for example, to produce load- and weight-optimized components, especially in lightweight construction. By deliberately varying the size of the rolling gap between a pair of rollers, a metal strip is produced that has various sections with different strip thicknesses along its length. The transitions between the different thickness sections can have different pitches. DE 38 07 399 A1 discloses a method for controlling the gap width of the rolling gap between the work rolls of a cold rolling stand for producing a metal strip, and an apparatus for carrying out the method. The control is based on measurement signals of the strip speed at the inlet and outlet and the strip thickness at the inlet and outlet. It is considered disadvantageous that the response times and control times are too long to obtain a sufficiently good thickness transition, especially in the transition areas, or that short transitions cannot be achieved at all.

[0004] To solve the problems arising from the response and correction times of the control system, EP 3 097 992 A1 describes a method for maintaining constant, or at least nearly constant, the forces exerted by each work roll on the metal strip, regardless of changes in the roll gap. This is achieved, inter alia, by controlling the strip tension acting on the metal strip. The strip tension is controlled by varying the reel speeds of the decoiler (from which the rolled strip is unwound) and the coiler (on which the rolled strip is wound). It is considered particularly advantageous to control the speeds of the work rolls and / or their rotational speeds, as well as the decoiler and / or coiler rotational speeds, according to precalculated data. This avoids control problems due to response and control times. However, this method has the disadvantage that a large amount of data must first be empirically recorded before a sufficient basis is available for calculating the necessary process parameters for each coiler roll and each work roll speed, which vary depending on the metal strip.

[0005] US 9,242,284 A1 describes a method for stretching a rolled metal strip, in which the metal strip is stretched between two linear actuators, and the rolling and stretching steps can be combined by also placing a roll stand between the two linear actuators. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Publication DE 38 07 399A1 [Patent Document 2] EP 3 097 992A1 publication [Patent Document 3] US9, 242, 284A1 publication Summary of the Invention [Problem to be solved by the invention]

[0007] On the other hand, the present invention aims to solve the problem of providing a rolling apparatus of the type mentioned at the beginning, which makes it possible to roll the material to be rolled flexibly, so that the disadvantages described in the previously known step rolling methods do not exist, or at most exist to a lesser extent. [Means for solving the problem]

[0008] This problem is solved according to the invention by a device according to claim 1 and a method according to claim 15. References here and hereinafter to rolled material refer in particular, but not exclusively, to rolled material in the form of metal strip. The present invention is also suitable for rolling, in particular step rolling, slabs or other non-strip-shaped rolled material into plates.

[0009] Here and hereafter, the term linear actuator is used to mean a drive for a rolled material that transmits the drive force to the rolled material over a longer curved portion of the drive, as opposed to a drive by individual rollers or rolls that transmit the drive force to the rolled material through their curved surfaces. Suitable linear actuators are disclosed, for example, in US Pat. No. 9,242,284 B2. It has surprisingly been found that measuring and controlling the tensile stress acting on the rolled material instead of its thickness can lead to very good rolling results. By controlling the tensile stress in the cross section of the rolled material, it is possible to directly and significantly influence the flow of the rolled material caused by the pressure exerted by the rolls in the roll gap, and thus the thickness reduction achievable by rolling. At the same time, it is possible to significantly optimize the flow of the microstructure in the roll gap and thus the quality of the rolled material. This is made possible in particular by the use of linear actuators, which allow for the introduction of sufficiently high tensile stresses into the rolled material. The aim is to keep the tensile stress exerted by the linear actuators on the rolled material as constant as possible, in particular regardless of the driving speed of the linear actuators. However, it can also be beneficial to control the tensile force in relation to the size of the rolling pass.

[0010] By controlling the tensile stress applied to the rolled material by the at least one linear actuator in relation to the determined tensile stress data, it is possible to keep the tensile stress constant, especially during the production of step-rolled sheet, where the strip speed downstream of each roll is constantly changing due to the constantly changing thickness reduction, and the control is preferably carried out only in relation to the determined tensile stress, and the conveying speed of the rolled material is adjusted accordingly so that the tensile stress acting on the rolled material is maintained.

[0011] In a preferred embodiment of the present invention, the control device is designed to determine and / or adjust the torque acting on the linear actuator in order to determine and / or adjust the tensile stress acting on the rolled material. For example, the torque acting on the linear actuator, and therefore the tensile stress applied to the rolled material, can be determined by the driving speed of the linear actuator and the power consumed by the linear actuator. Therefore, the power of the linear actuator, and therefore the tensile stress acting on the rolled material, can be controlled by the control device. In this regard, it is preferable that the control device has means for determining the power consumption and driving speed of the linear actuator, and is designed to determine and / or set the tensile stress based on the determined information.

[0012] For this purpose, servo motors, preferably two servo motors for each of the upper and lower drives of the linear actuators, are particularly suitable. The servo motors allow for high-performance driving. Since the linear actuators allow the workpiece to be synchronized without relative movement, changes in the torques generated by the servo motors are transmitted to the workpiece without delay. This is particularly advantageous in step rolling, as it allows for relatively short transitions between regions of different thicknesses of the workpiece.

[0013] Alternatively or additionally, the device according to the present invention may include force measuring bearings in the bearings of the linear actuator and / or the pair of rolls, in particular in the bearings of the drive shafts of the linear actuator, to determine the tensile stress applied to the rolled material. Such force measuring bearings are well known. For example, they may be designed so that a gap is provided in the bearing shell of the rolling bearing and strain gauges are attached on both sides of the gap, thereby making it possible to measure changes in the gap width due to changes in the tensile stress introduced into the rolled material. Such force measuring bearings are preferably used, for example, to support the drive shafts of the linear actuators, and in this case, the drive motors for driving the drive shafts supported in this way are preferably directly connected to the drive shafts without an intervening gearbox. The use of force measuring bearings enables high-performance measurement of the tensile stress in the rolled material.

[0014] In principle, it is advantageous if the means for detecting tensile stresses and / or the control system are designed to measure the stress distribution across the width of the rolled material, and in particular if the tensile stresses are measured on both sides of the longitudinal direction of the rolled material, it is possible to satisfactorily determine the tensile stress distribution across the width of the rolled material. In order to optimize the flow of the rolled material in the roll gap, it is also advantageous if the control device is connected to a means for adjusting the contact pressure between the pair of rolls, which makes it possible to control all forces acting on the rolled material in the roll gap.

[0015] A further preferred embodiment of the present invention is characterized in that at least one linear actuator has at least one adjusting device, by means of which the position of the linear actuator relative to the workpiece can be changed during operation, in particular by pivoting it about an axis substantially perpendicular to the drive direction of the workpiece. By pivoting the linear actuator, it is possible to change and adjust the tensile stress distribution across the width of the workpiece. This makes it possible, for example, to correct sabers formed in the workpiece during rolling at an early stage, in particular if the adjusting device is connected to a control device and is driven in relation to the tensile stress distribution measured across the width of the workpiece. Due to the adjustability of the linear actuator(s), the device according to the present invention can be used not only for rolling but also for straightening the workpiece at the same time.

[0016] It is preferable that the linear actuator be able to oscillate on a curved path. It is significant that the position of the linear actuator relative to the strip can be adjusted even during rolling. Furthermore, the radius of curvature of the path itself can also be adjusted during rolling. This can be applied to both linear actuators when one linear actuator is provided upstream and the other downstream with respect to the driving direction of a pair of rolls. For this purpose, the at least one upper drive unit and the at least one lower drive unit, which are typically provided in a linear actuator and act on the workpiece from above and below, are each held in a frame, and the upper and lower drive units of the linear actuator can be positioned within a fixed frame relative to the frame. It is more preferable that at least one first adjustment device for the upper and lower drive units is provided on one side of the workpiece to allow the upper and lower drive units to be displaced in a direction perpendicular to the drive direction, and that at least one second adjustment device for the upper and lower drive units is provided on the other side of the workpiece to allow the upper and lower drive units to be rotated about a substantially vertical axis. Therefore, the drive direction of the linear actuator can be adjusted relatively freely relative to the longitudinal direction of the workpiece.

[0017] It is advantageous if the linear actuator can be pivoted at an angle of at least ±10 degrees, preferably ±20 degrees, relative to the longitudinal direction of the workpiece, in particular to enable straightening of the workpiece. In order to ensure the highest possible tensile stress, it is advantageous if the upper and lower drives of the linear actuator have a number of contact elements arranged successively one behind the other in the rolling direction for contacting the rolled material, each of which is preferably designed elastically to ensure reliable contact with the rolled material even if the rolled material has different thicknesses in the rolling direction.

[0018] Alternatively, at least one of the linear actuators may comprise a non-contact eddy current drive for driving the workpiece without contact. A measuring device, in particular a laser measuring device, is preferably provided downstream of the pair of rolls in the rolling direction to measure the thickness and / or speed of the rolled material. It is also possible to design this measuring device or provide separate measuring devices downstream of the pair of rolls to determine the flatness, waviness and sabre degree of the rolled material in the driving direction. All determined measurement data can also be used to control the tensile stress.

[0019] In yet another embodiment of the present invention, linear actuators are provided before and after each of a pair of rolls in the rolling direction, and each of the linear actuators is suitable for jointly applying tension to the rolled material, for example, by the linear actuator provided upstream of the pair of rolls in the drive direction braking the rolled material and the linear actuator provided downstream pulling the rolled material. [Effects of the Invention]

[0020] As is already clear from the above, the problem underlying the present invention is solved by a method for rolling a rolled material using an apparatus according to the present invention, in which the rolled material is rolled by a pair of rolls, a linear actuator provided downstream of the pair of rolls in the rolling direction cooperates with the pair of rolls and / or a linear actuator provided upstream of the pair of rolls in the rolling direction to impart a tensile stress to the rolled material, and the tensile stress imparted to the rolled material by the linear actuator is controlled. In a special embodiment of the method according to the invention, the height of the roll gap is varied in connection with a control device.

[0021] In order to correct the rolled material or minimize or avoid serrations, it is preferable to change the direction of the tensile stress imparted to the rolled material by the linear actuator in a controlled manner relative to the longitudinal direction of the rolled material. The device according to the invention can also be used to carry out a rolling process in which the rolled material passes alternately between pairs of rolls in opposite directions, in other words, the device according to the invention makes it possible to roll at least individual parts of the rolled material in a reversing mode, in particular (but not exclusively) when linear actuators are provided upstream and downstream of the roll gap, respectively. Advantageously, this method makes it possible to control the tensile stress so as to cause at least 50% of the deformation of the rolled material in the roll gap. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a side view of the basic structure of a rolling line according to the invention; FIG. [Figure 2] 2 is a partial cross-sectional side view showing the basic structure of the linear actuator 4 shown in FIG. 1. [Figure 3a] 1 is a schematic diagram showing the behavior of each elastic contact element of a linear actuator in a driving zone upstream of a pair of rolls in a rolling line using a metal strip having a uniform thickness. [Figure 3b] 1 is a schematic diagram showing the behavior of each elastic contact element of a linear actuator in a driving zone downstream of a pair of rolls in a rolling line using a step-rolled metal strip. FIG. [Figure 4a] 1 is a schematic diagram showing a linear actuator in the form of an eddy current drive in a driving zone upstream of a pair of rolls of a rolling line using a metal strip having a uniform thickness. [Figure 4b] 1 is a schematic diagram showing a linear actuator in the form of an eddy current drive in a drive zone downstream of a pair of rolls of a rolling line using step-rolled metal strip. [Figure 5] 2 is a schematic cross-sectional view showing the basic structure of the linear actuator 4 shown in FIG. [Figure 6] 6 is a top view, partially in section, of the actuator of the linear actuator of FIGS. 2 and 5. FIG. [Figure 7a]6 is a top view, partially in section, of the linear actuator of FIGS. 2 and 5 in a first operating position. FIG. [Figure 7b] 6A and 6B are top, partially cross-sectional views of the linear actuator of FIGS. 2 and 5 in different operating positions. [Figure 8] Similar to FIG. 5, but here showing the basic structure of a linear actuator with an eddy current drive. DETAILED DESCRIPTION OF THE INVENTION

[0023] The present invention will now be described in more detail with reference to the drawings, which illustrate preferred embodiments of the invention. 1 shows a rolling and stretching line according to the invention, which comprises a roll stand 3 with a pair of rolls 1 and 2, a linear actuator 4 upstream of the roll stand 3 in the direction of strip travel, and a linear actuator 5 downstream of the roll stand 3, which is particularly suitable for step-rolling hot- or cold-rolled metal strip. A measuring device 6 is provided upstream of the linear actuator 4 in the direction of strip travel, and a measuring device 7 is provided downstream of the linear actuator in the direction of strip travel. These measuring devices 6 and 7 are intended to determine, in particular, the strip speed and the flatness, uniformity, maneuverability, and sabre of a metal strip 8 guided through the rolling and stretching line. The line terminates in a coiler 9, on which the rolled metal strip 8 is wound.

[0024] As can be seen particularly in Figure 2, linear actuator 4 has an upper drive with circulating chain 11, which is shown only diagrammatically in Figure 2, and a lower drive with circulating chain 12. Correspondingly, linear actuator 5 has an upper drive with circulating chain 13 and a lower drive with circulating chain 14. Circulating chains 11, 12, 13, 14 circulate on chain rails 12a, 14a and are driven by two servo motors 15, 16, 17, 18, respectively, which are disposed on either side of drive shafts 21, 22, 23, 24 of the respective drives and transmit drive torque to each circulating chain 11, 12 via gears 25, 26. Each drive shaft 21, 22, 23, 24 is mounted on chain rails 12a, 14a.

[0025] The metal strip 8 is guided between the upper and lower circulating chains 11, 12, 13, 14 of the linear actuators 4, 5. Each chain link of the circulating chains 11, 12 is provided with a contact element 27, 28, which is designed to be elastic so that it can firmly grip the metal strip even if the thickness of the metal strip varies over the length of the contact area of ​​the linear actuators 4, 5, as can be seen in particular from the illustrations in Figures 3a (showing a uniformly rolled metal strip 8) and 3b (showing a stepped rolled metal strip 8). Similarly, relatively stiff contact elements mounted by springs can be used, provided that the springs are designed to be sufficiently stiff for the mounting.

[0026] As an alternative to contact linear actuators, non-contact linear actuators can also be used, in particular eddy current linear actuators, in which the chain links have magnets. Because of their non-contact nature, these actuators can easily drive metal strips whose thickness varies along their length. Figures 4a and 4b show how a metal strip 8 is guided between the magnets or electric coils 35, 36 of the upper and lower drive units of an eddy current linear actuator, with the metal strip 8 shown in Figure 4a being flat-rolled and the metal strip 8 shown in Figure 4b being stepped-rolled. In this embodiment, the tensile stress in the metal strip 8 is generated by the tension applied by the linear actuator 5 and the counter-tension applied by the linear actuator 4. For this purpose, each linear actuator 4, 5 is technically identical, but is installed in line rotated by 180 degrees so that each motor is located on the side of the respective linear actuator 4, 5 facing away from the roll stand 3.

[0027] The tensile stress applied to the metal strip 8 is determined by respective force measuring bearings 31, 32, which are arranged on either side of the drive area of ​​the linear actuators 4, 5 defined by the respective circulating chains 11, 12 as can be seen in FIG. 2.

[0028] FIG. 5 particularly illustrates the operation of each positioning device for positioning the linear actuator 4 shown in FIG. 2. The linear actuator 4 has a fixed frame 41 with lateral struts 42, 43. As can be seen particularly in the cross-sectional view of FIG. 6, rotating struts 44, 45 are attached to the lateral struts 42, 43. Each of the rotating struts 44, 45 has an outer wall 46 that opens on opposite sides along its length, as can be seen in FIG. 6. In this portion, the inner wall of each rotating strut 44, 45 is formed as a guide 47. Actuators 48, 49 are provided at the lower end of each rotating strut 44, 45 to rotate the corresponding rotating strut. The angular position of each rotating strut 44, 45 is adjustable over a relatively wide range (two possible adjustment positions are shown in FIG. 6).

[0029] The upper drive is supported by an upper cross beam 51, and the lower drive by a lower cross beam 52. Guide posts 53, 54 are provided on the lower cross beam on both sides adjacent to each circulating chain 11, 12, on which the upper cross beam 51 is mounted so as to be vertically movable. The upper cross beam 51 can be positioned vertically relative to the lower cross beam 52 by hydraulic cylinders 55, 56 supported on the upper part of the frame 41. The lower cross beam 52 is supported on plain bearings 57, 58 provided below the lower cross beam 52 in the area of ​​the guide posts 53, 54. The guide posts 53, and therefore the entire linear actuator, can be adjusted in a direction perpendicular to the conveying direction by means of an actuator 59, the drive rod of which is connected to the guide posts 53 via an actuator.

[0030] At each end of the upper cross beam 51 and the lower cross beam 52, there are provided support rollers 61, 62, 63, 64, which are guided in the horizontal plane into guides 46, 47 of the rotating posts 44, 45. The support rollers 61, 62 of the upper cross beam 51 are vertically displaceable on the rotating posts 44, 45. The combination of the actuators 48, 49, which can adjust the position of the guides of the rotary columns 44, 45, and the actuator 59, which acts in a direction perpendicular to the conveying direction, makes it possible to rotate the entire linear actuator on a substantially partially circular path portion around an imaginary center point in the center of the rolled material, and the radius of the imaginary circular path portion or the position of the imaginary center circle can be adjusted within a wide range, in particular so that the imaginary center point M can be located on both sides of the linear actuator. As a result, it is possible to position the imaginary center point upstream of the respective linear actuator in the conveying direction, as shown in Figures 7a and 7b, and to guide the rolled material through the rolling line in opposite conveying directions, i.e., in a reversing operation.

[0031] The basic structure of the linear actuator shown in Fig. 8 basically corresponds to the basic structure of the linear actuator shown in Fig. 5. The only difference is that while each circulating chain 11, 12 has a contact element that contacts the workpiece in the drive device shown in Fig. 5, here each circulating chain has a magnet or an electric coil 71, 72, so that the workpiece can be transported between each circulating chain without contact. [Industrial Applicability]

[0032] INDUSTRIAL APPLICABILITY The present invention relates to a rolling mill and a rolling method using the rolling mill, and therefore has wide industrial applicability. [Explanation of symbols]

[0033] 1 roll 2 rolls 3 Roll Stand 4 Linear Actuators 5 Linear Actuators 6. Measuring equipment 7. Measuring equipment 8 Metal strip 9 Coiler device 11 Circulating Chain 12 Circulating Chain 12a chain rail 13 Circulating Chain 14 Circulating Chain 14a chain rail 15 Servo motor 16 Servo motors 17 Servo motor 18 Servo motor 21 Drive shaft 22 Drive shaft 23 Drive shaft 24 drive shaft 25 Gears 26 Gears 27 Contact Elements 28 Contact Elements 31 Force measuring bearing 32 Force measuring bearing 35 Magnet or electric coil 36 Magnet or electric coil 41 Fixed Frame 42 Each post 43 Each pillar 44 Rotating Pillar 45 Rotating Pillar 46 Exterior Wall 47 Guide 48 Actuator 49 Actuators 51 Upper cross beam 52 Lower cross beam 53 Guide pillar 54 Guide pillar 55 Hydraulic cylinder 56 Hydraulic cylinder 57 Plain bearings 58 Plain bearing 59 Positioning cylinder 61 Support roller 62 Support roller 63 Support roller 64 Support roller 71 Magnet or electric coil 72 Magnet or electric coil

Claims

1. An apparatus for rolling a material to be rolled, An apparatus having at least one pair of rolls and at least one linear actuator (4, 5) provided downstream of the pair of rolls in the rolling direction and capable of applying tensile stress to the rolled material together with the pair of rolls, means for detecting the tensile stress; In order to change the tensile stress applied to the rolled material or to keep the tensile stress constant downstream of the roll gap even when the driving speed is changed, a control device that controls a driving force of the linear actuator in relation to the detected tensile stress, The material to be rolled is a metal strip, 1. The device, characterized in that the at least one linear actuator (4, 5) comprises at least one adjustment device capable of changing the position of the linear actuator relative to the metal strip during operation, thereby changing and adjusting the tensile stress distribution across the width of the metal strip.

2. 2. Device according to claim 1, characterized in that the control device is designed to determine and / or regulate the torque acting on the linear actuators (4, 5).

3. 3. The device according to claim 2, characterized in that the control device comprises means for determining the power consumption and the drive speed of the linear actuators (4, 5) and is designed to determine and / or set the torque from the determined information on the power consumption and the drive speed.

4. An apparatus as described in any one of the preceding paragraphs, characterized in that it comprises force measuring bearings in the linear actuators (4, 5) and / or in the bearings of the pair of rolls, respectively, for determining the tensile stress applied to the metal strip.

5. 5. The device according to claim 4, wherein each of said force measuring bearings is mounted in a bearing portion of a drive shaft of a linear actuator (4, 5).

6. 10. The device according to claim 1, wherein the means for detecting the tensile stress and / or the control device are designed to measure the tensile stress distribution across the width of the metal strip.

7. The control device is connected to each means for adjusting the contact pressure of the pair of rolls.

10. The device according to any one of the preceding claims, characterized in that

8. 2. The device according to claim 1, characterized in that by means of at least one adjusting device the position of at least one linear actuator (4, 5) can be rotated about an axis substantially perpendicular to the driving direction.

9. 9. The device according to claim 8, characterized in that the linear actuators (4, 5) act on the metal strip from above and below, respectively, and have upper and lower drives held in a frame (41), the upper and lower drives being positionable relative to the frame within the fixed frame.

10. The device described in claim 9, characterized in that at least one first adjustment device for the upper and lower drive devices is provided on one side of the metal strip, using which the upper and lower drive devices can be displaced in a direction perpendicular to the drive direction, and at least one second adjustment device for the upper and lower drive devices is provided on the opposite side of the metal strip, using which the upper and lower drive devices can be rotated around an axis substantially perpendicular to the drive direction and a direction perpendicular to the drive direction.

11. 11. Apparatus according to any one of claims 8 to 10, characterized in that the adjustment device is configured to allow the linear actuator to pivot at least ±10 degrees.

12. 12. The apparatus of claim 11, wherein the adjustment device is configured to allow the linear actuator to rotate at least ±20 degrees.

13. 13. The device according to claim 9, wherein the upper and lower drives of the linear actuators (4, 5) have a plurality of contact elements (27, 28) arranged successively one behind the other in the rolling direction for contacting the metal strip, the contact elements (27, 28) being formed elastically to ensure contact with the metal strip even if the metal strip has a different thickness in the rolling direction.

14. 13. Apparatus according to any one of claims 1 to 12, characterized in that at least one of the linear actuators (4, 5) comprises one or more non-contact eddy current drives for driving or braking the metal strip without contact.

15. An apparatus as described in any one of claims 1 to 12, characterized in that it has at least one measuring device (6, 7) downstream of the pair of rollers in the rolling direction for measuring the thickness and / or speed of the metal strip.

16. 16. The device according to any one of claims 1 to 15, characterized in that it comprises one linear actuator (4, 5) upstream of said pair of rollers in the rolling direction and one linear actuator (4, 5) downstream of said pair of rollers in the rolling direction.

17. 17. A method for rolling the metal strip using the apparatus according to any one of claims 1 to 16, characterized in that the metal strip is rolled by the pair of rolls, a linear actuator (4, 5) provided downstream of the pair of rolls in the rolling direction imparts a tensile stress to the metal strip by cooperating with the pair of rolls and / or a linear actuator (4, 5) provided upstream of the pair of rolls in the rolling direction, and the tensile stress imparted to the metal strip by the linear actuator (4, 5) is controlled.

18. 18. The method of claim 17, wherein the roll gap height is varied in conjunction with the control device during rolling.

19. 19. A method according to claim 17 or 18, characterized in that the direction of the tensile stress applied to the metal strip by the linear actuators (4, 5) is changed in a controlled manner relative to the longitudinal direction of the metal strip in order to straighten the metal strip or to minimize or avoid sabre errors.

20. 20. The method according to any one of claims 17 to 19, characterized in that the metal strip passes alternately between the pair of rolls in opposite directions.

21. 21. The method according to any one of claims 17 to 20, characterized in that the tensile stress is controlled to cause a deformation of the metal strip in the roll gap of at least 50%.

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