Patent Application
20220402007
The present invention relates to a device for rolling, in particular for stepped rolling, of rolling stock with at least one pair of rolls and at least one linear drive arranged downstream of the pair of rolls in the rolling direction, which together with the pair of rolls can apply tensile stress to the rolling stock, and with means for detecting the tensile stress. The invention also relates to a method for rolling the rolling stock with such a device.
Devices for rolling and straightening metal strips are used in rolling, straightening and processing lines for metal strips. Metal strips are rolled and straightened for different purposes. In rolling, the strip is deformed by horizontal force and thereby rolled thinner. In straightening, the strip is straightened by tension. In stretch straightening in particular, the attempt is made to keep the section of strip to be subjected to tension as small as possible. The smaller the area of deformation, the more balanced the microstructure.
A special form of rolling is stepped rolling, also known as “flexible rolling”. It is used to produce, for example, load- and weight-optimized components, especially in lightweight construction. By deliberately changing the size of the rolling gap between a pair of rolls, a metal strip is produced which has various sections of different strip thicknesses along its length. The transition sections between strip sections of different thicknesses can have different inclinations.
The publication 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 the production of strips of metal as well as a device for carrying out the method. The control is based on the signals of the measurement of the strip speed on the inlet side and on the outlet side as well as the strip thickness on the inlet side and on the outlet side. The control is considered to be disadvantageous in that the response and control times are too long to achieve sufficiently good thickness transitions, particularly in the transition sections, or to realize short transitions at all.
In order to solve the problems arising from the response of the control system and the necessary control times until correction, EP 3 097 992 A1 describes a method in which the forces applied to the metal strip by the work rolls are kept constant or at least approximately constant irrespective of a change in the size of the roll gap. This is to be achieved in particular by controlling the strip tension forces acting on the metal strip. The strip tension is controlled by changing the rotational speeds of a decoiler device, from which the strip to be rolled is unwound, and a coiler device, onto which the rolled strip is rewound. It is considered particularly advantageous if the speed of the work rolls and/or the rotational speed of the work rolls as well as the rotational speeds of the decoiler device and/or the coiler device are controlled according to precalculated data. This is to avoid the disadvantages of control by response time and control time. This method appears to be disadvantageous in that a large number of data must first be empirically recorded before a sufficient basis is available for calculating the necessary process parameters for the speeds of the coiler and work rolls, the process parameters changing for each metal strip.
U.S. Pat. No. 9,242,284 A1 describes a process for stretching rolled metal strip in which the metal strip is stretched between two linear drives. A roll stand can also be arranged between the two linear drives, so that it is possible to combine the rolling and stretching steps.
The present invention, in contrast, is intended to solve the problem of providing a rolling device of the type mentioned at the beginning, with which it is possible to roll stock flexibly, whereby the disadvantages mentioned of previously known processes for stepped rolling do not exist or at most exist to a lesser extent.
This task is solved according to the invention with a device according to claim 1 and a method according to claim 15.
When rolling stock is referred to here and in the following, this refers in particular, but not exclusively, to rolling stock in the form of metal strip. The claimed invention is also suitable for rolling, and in particular stepped rolling, slabs into thick plates or other non-strip rolling stock.
When the term linear drive is used here and in the following, it refers to a drive for the rolling stock that transmits the drive forces to the rolling stock over a longer straight section of the drive, unlike a drive by means of rollers or rolls, where the drive forces are transmitted to the rolling stock over their curved surface. A suitable linear drive is disclosed, for example, in U.S. Pat. No. 9,242,284 B2.
It was surprisingly found that it is possible to achieve very good rolling results if the tensile stress acting on the rolling stock is measured and controlled instead of the thickness of the rolling stock. By controlling the tensile stress in the cross-section of the rolling stock, it becomes possible to directly and significantly influence the flow of the rolling stock initiated by the pressure exerted by the rolls in the roll gap, and thus the reduction in thickness that can be achieved by rolling. At the same time, the flow of the microstructure in the roll gap and thus the quality of the rolling stock can be significantly optimized. This is made possible in particular by the use of a linear drive, since sufficiently high tensile stresses can be introduced into the rolled material with a linear drive. In particular, the aim is to keep the tensile stress applied to the rolling stock by the linear drive as constant as possible, regardless of the drive speed of the linear drive. However, it can also be useful to control the tension as a function of the size of the rolling pass.
By controlling the tensile stress to be applied to the rolling stock by the at least one linear drive as a function of determined tensile stress data, it is possible to keep the tensile stress constant, in particular during the production of step-rolled sheets, in the production of which the strip speed behind the rolling rolls changes constantly due to the constantly varying change in thickness reduction. The control is preferably carried out exclusively as a function of the tensile stress determined and regulates the transport speed for the rolling stock accordingly so that the tensile stress acting on the rolling stock is maintained.
In a preferred embodiment of the invention, the control device is designed to determine and/or adjust the torque acting in the linear drive in order to determine and/or adjust the tensile stress acting on the rolling stock. For example, the torque acting in the linear drive and thus the tensile stress applied to the rolling stock can be determined from the drive speed of the linear drive and the power absorbed by the linear drive. Accordingly, the power of the linear drive can be controlled by the control device and thus the tensile stress acting on the rolling stock. In this respect, it is preferred if the control device has means for determining the power consumption and the drive speed of the linear drive and is designed to determine and/or set the tensile stress from the determined information.
Servo motors, preferably two each for the upper and lower drive of a linear drive, are particularly suitable for this purpose. They enable a highly dynamic drive. Since the linear drives allow the rolling stock to be entrained without relative movements, changes in the torques generated by the servomotors are transmitted to the rolling stock without delay. In stepped rolling, among other things, this has the advantage that the transitions between areas of different thickness of the rolling stock can be comparatively short.
Alternatively or in addition thereto, the device according to the invention has force measuring bearings in the bearing of the linear drive and/or of the pair of rolls, in particular in the bearing of the drive shafts of the linear drive, for determining the tensile stress applied to the rolling stock. Such force measuring bearings are sufficiently well known. They can be designed, for example, in such a way that a gap is provided in a bearing shell of a rolling bearing and a strain gauge is attached to both sides of the gap so that a change in the gap width due to a change in the tensile stress introduced into the rolling stock can be measured. Such force measuring bearings can, for example, preferably be used to support the drive shafts of linear drives, in which case, moreover, the drive motor or motors for driving a drive shaft supported in this way are preferably connected directly to the drive shaft without the interposition of a gearbox. With force measuring bearings, highly dynamic measurement of the tensile stress in the rolled material is possible.
In principle, it is advantageous if the means for detecting the tensile stress and/or the control system are designed to measure the stress distribution over the width of the rolling stock. In particular, if the tensile stress is measured on both longitudinal sides of the rolling stock, the tensile stress distribution over the width of the rolling stock can be determined in a sufficient manner.
In order to optimize the flow of the rolling stock in the roll gap, it is also advantageous if the control device is coupled with means for adjusting the contact pressure of the roll pair. This makes it possible to control all forces acting on the rolling stock in the roll gap.
A further preferred embodiment of the invention is characterized in that the at least one linear drive has at least one adjusting device by means of which the position of the linear drive relative to the rolling stock can be changed during operation and, in particular, can be pivoted about an axis essentially orthogonal to the drive direction of the rolling stock. By pivoting the linear drive, it is possible to change and adapt the tensile stress distribution across the width of the rolling stock. This makes it possible, for example, to compensate at an early stage for a saber forming in the rolling stock during rolling, in particular if the adjusting device is coupled to the control device and the adjusting device is actuated as a function of the tensile stress distribution measured across the width of the rolling stock. Due to the adjustability of the linear actuator(s), the device according to the invention can be used not only for rolling but also for straightening the rolling stock at the same time.
It is preferred if the linear drive can be swiveled on a curved path. It makes sense that the position of the linear drive relative to the strip can also be adjusted during rolling. Furthermore, the radius of curvature of the path itself can be variable during rolling. This can also apply to both linear drives if one linear drive is arranged upstream and one downstream of the pair of rolls in the drive direction.
For this purpose, the at least one upper and the at least one lower drive, which are typically provided in a linear drive and act on the rolling stock from above and below, respectively, are held in a frame, wherein the upper and lower drives of the linear drive can be positioned within the fixed frame relative to the frame. In this context, it is furthermore preferred if at least one first adjusting device for the upper and lower drive is provided on one side of the rolling stock, by means of which the upper and lower drive can be displaced in a direction transverse to the drive direction, and at least one second adjusting device for the upper and lower drive is provided on the opposite side of the rolling stock, by means of which the upper and lower drive can be pivoted about a substantially vertical axis. Thus, the drive direction of the linear drive is comparatively freely adjustable relative to the longitudinal direction of the rolling stock.
In particular, to enable straightening of the rolling stock, it is advantageous if the linear drive can be pivoted by an angle of at least +/−10°, preferably at least +/−20°, relative to the longitudinal direction of the rolling stock.
In order to ensure the highest possible tensile stresses, it is advantageous if the upper and lower drives of the linear drive have several contact elements arranged one behind the other in the rolling direction for contacting the rolling stock, the contact elements preferably being designed to be elastic in such a way that they contact the rolling stock reliably even if it has different thicknesses in the rolling direction.
Alternatively, at least one of the linear drives can have a non-contact eddy current drive that drives the rolling stock without contact.
Preferably, a measuring device, in particular a laser-based measuring device, is provided downstream of the pair of rolls in the rolling direction for measuring the thickness and/or the speed of the rolling stock. In addition, this measuring device can be designed or further measuring devices can be provided to determine the flatness, waviness and/or saber of the rolling stock in the drive direction behind the pair of rolls. All the measurement data determined can also be used to control the tensile stress.
In yet another embodiment according to the invention, a linear drive is provided in each case in front of and behind the pair of rolls in the rolling direction, which are suitable for jointly applying tension to the rolling stock, for example in that the linear drive arranged in front of the pair of rolls in the drive direction brakes the rolling stock, while the linear drive arranged behind pulls the rolling stock.
As can already be seen from the above, the task underlying the invention is solved with a method for rolling a rolling stock with a device according to the invention in that the rolling stock is rolled by the pair of rolls, wherein a tensile stress is applied to the rolling stock by a linear drive arranged downstream of the pair of rolls in the rolling direction in cooperation with the pair of rolls and/or a linear drive arranged upstream of the pair of rolls in the rolling direction, and wherein the tensile stress exerted on the rolling stock by the linear drive is controlled.
In a particular embodiment of the process according to the invention, the height of the roll gap is changed as a function of the control device.
It is also preferred that the direction of the tensile stress exerted by the linear drive on the rolling stock is changed in a controlled manner relative to the longitudinal direction of the rolling stock in order to straighten the rolling stock or to minimize or avoid a saber error.
With the device according to the invention, a rolling process is also possible in which the rolling stock passes through the pair of rolls alternately in opposite directions. In other words, the device according to the invention makes it possible to roll in reversing mode for at least individual sections of the rolling stock, in particular, but not exclusively, if a linear drive is provided in each case upstream and downstream of the roll gap.
With the process, it is possible and useful to control the tensile stress in such a way that it causes at least 50% of the deformation of the rolled material in the roll gap.
In the following, the invention is explained in more detail with reference to figures showing preferred embodiments of the invention.
As can be also seen in particular in
The metal strip 8 is guided between the upper and lower circulating chains 11, 12, 13, 14 of the linear drives 4, 5. Contact elements 27, 28 are arranged on the chain links of the circulating chains 11, 12, the contact elements being of elastic design so that they can grip a metal strip firmly even if the thickness of the metal strip changes over the length of the contact area of the linear drive 4, 5, which can be seen in particular from the illustrations in
As an alternative to contact-based linear drives, it is also possible to use contactless linear drives, in particular eddy current-based linear drives, whose chain links are provided with magnets. Since the drive is contactless, a metal strip with a thickness that varies along its length can also be driven linearly without any problems.
In this embodiment, the tensile stress in the metal strip 8 is generated by a tension applied by the linear drive 5 and a counter-tension applied by the linear drive 4. The linear drives 4 and 5 are technically identical for this purpose, but are installed in the line rotated by 180° so that the motors are each located on the side of the respective linear drive 4, 5 facing away from the roll stand 3.
The tensile stress applied in the metal strip 8 is determined by means of force measuring bearings 31, 32, which, as can be seen in
The upper drive is held by an upper cross member 51 and the lower drive by a lower cross member 52. On both sides next to the circulating chains 11, 12, guide pillars 53, 54 are located on the lower cross member, on which the upper cross member 51 is mounted so that it can be moved vertically. The upper cross member 51 can be positioned vertically relative to the lower cross member 52 by means of hydraulic cylinders 55, 56, which are supported at the top of frame 41. The lower cross member 52 is supported on sliding bearings 57, 58 provided in the area of the guide pillars 53, 54 under the lower cross member 52. The guide pillar 53 and thus the entire linear drive can be adjusted transversely to the transport direction by means of an actuator with an actuator 59, the drive rod of which is connected to the guide pillar 53.
Support rolls 61, 62, 63, 64 are provided at the ends of the upper cross member 51 and the lower cross member 52 and are guided in a horizontal plane in the guides 46, 47 of the rotary columns 44, 45. The support rolls 61, 62 of the upper cross member 51 are vertically displaceable in the rotary columns 44, 45.
In combination with the actuators 48, 49, with which the position of the guides of the rotary columns 44, 45 can be adjusted, and the actuator 59 acting transversely to the transport direction, it is possible to pivot the entire linear drive on an essentially part-circular path section about a virtual center point, which lies in particular in the center of the rolling stock, the radius of the virtual circular path section or the position of the virtual center point being adjustable within wide limits, in particular in such a way that the virtual center point M can lie on both sides of the linear drive. As a result, it is possible in particular to place the virtual center point in front of the respective linear drive in the transport direction, as shown in
The basic structure of a linear drive shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2019 131 761.4 | Nov 2019 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/DE2020/100994 | 11/24/2020 | WO |
