Method, device and computer program for adjusting the distribution of strip tension when reeling up a cold-rolled metal strip

Abstract

The invention relates to a method, a device and a computer program for adjusting the distribution of strip tension when reeling up a cold-rolled metal strip (5) using a wind-up device (140) to form a coil. The method comprises the following steps: - detecting the distribution of the current strip tension over the width of the metal strip when reeling up the strip (5) upstream of the wind-up device (140); and - adjusting the distribution of the current strip tension to a specified distribution of the target strip tension over the width of the metal strip (5) by suitable variation of at least one control variable, wherein the distribution of the target strip tension over the width of the metal strip (5) is adapted during reeling-up in consideration of a distribution of the winding diameter W of the coil over its width that changes when reeling up. In order to improve the flatness of the metal strip (5) later unwound from the coil, according to the invention the distribution of the target strip tension over the width of the metal strip (5) is additionally adapted to the thickness distribution D of the metal strip (5) over its width during reeling-up.

Description

[0001] Method, device and computer program for controlling the distribution of strip tension during coiling of a cold-rolled metal strip

[0002] The invention relates to a method, a device, and a computer program for controlling the distribution of strip tension when coiling a cold-rolled metal strip into a coil using a coiling and rewinding device. The invention also relates to a system for implementing the method.

[0003] When winding strips that do not have a parallel profile in their lengthwise and / or widthwise direction, i.e. do not have a uniform cross-section, profile deviations increasingly accumulate. Reasons for the non-uniform cross-section can be the stiffness of the strip, residual moisture contained during winding and / or air that is wound along with the strip. The non-uniform cross-section leads to different winding diameters across the width of the metal strip and, as a result, to different tangential winding speeds at the contact points where two superimposed turns of the wound metal strip touch. These different tangential winding speeds are proportional to different strip tensions at the contact points, i.e. to an undesirable, and in particular non-constant, distribution of the actual strip tension across the width of the metal strip.This, in turn, leads to undesirable deviations in the actual flatness of the coiled and subsequently uncoiled metal strip from a specified target flatness. The problem becomes apparent after the coil is uncoiled, for example, during a reversing rolling process or at the end customer's site.

[0004] Numerous methods for controlling the flatness of a cold-rolled metal strip are known in the prior art. For example, Chinese patent application CN 102029294 A discloses a method for cold-rolling a steel strip using a cold rolling mill in which the thickness distribution of the metal strip is controlled in the width direction. CN 101618402 A discloses a controlled combination of a flatness feedforward control and a flatness control.

[0005] In order to achieve good flatness of the metal strip after unwinding the metal strip from a coil, it is important to first wind the metal strip onto the coil with a suitably specified, not necessarily constant, distribution of the strip tension across the width of the metal strip, which at least partially compensates for the undesirable distribution of the actual strip tension or its causes mentioned above.

[0006] Specifically, it is therefore already known in the prior art to regulate the distribution of the strip tension across the width of the metal strip according to the preamble of patent claim 1. A predetermined distribution of the desired strip tension across the width of the metal strip is repeatedly adapted during coiling to the changing distribution of the coil diameter across its width during coiling.

[0007] This known adjustment of the target strip tension of the metal strip does result in a certain improvement in the flatness of the unwound metal strip; however, the resulting flatness is still not satisfactory.

[0008] The invention is based on the object of further developing a known method and computer program product, a known device for regulating the distribution of strip tension during the coiling of a cold-rolled metal strip, and a known system with the device such that the flatness of the metal strip is improved after coiling and in particular after uncoiling, even if the cross-section varies in the width and length directions of the metal strip before coiling. The term "varying cross-section" refers, for example, to different crowning ranges, different wedge profiles, concave cross-sections, or cross-sections with a shifted center.

[0009] This object is achieved by the method claimed in claim 1. Accordingly, the method according to the invention is characterized in that the distribution of the desired strip tension across the width of the metal strip is adjusted during coiling, additionally taking into account a thickness distribution of the metal strip across its width.

[0010] The terms "profile," "thickness distribution across the width," and "cross-section across the width" of the metal strip are used synonymously. These parameters can also vary in the longitudinal direction of the metal strip.

[0011] The term “distribution of the strip tension over the strip width” also includes all physical quantities representing this term, such as the distribution of the tangential winding speed over the width.

[0012] The claimed additional consideration of the thickness distribution of the metal strip across its width when specifying the distribution of the target strip tension across the width of the metal strip during coiling enables and advantageously results in significantly improved compensation for the profile deviations that disadvantageously accumulate during the coiling of the metal strip. This improved compensation results in an improvement in the flatness of the metal strip, especially after it has been unwound from the previously coiled coil.

[0013] Conversely, a constant distribution of the target strip tension across the width of the metal strip would not result in the desired flatness of the metal strip if the coil diameter and / or thickness distribution of the metal strip were not constant across its width. A constant distribution of the target strip tension would only result in the desired flatness of the metal strip if the coil diameter and thickness distribution were constant.

[0014] Because each metal strip to be wound has an individual thickness distribution in the width direction, and this can also vary in the longitudinal direction of the strip, it is necessary that the distribution of the desired strip tension in the width direction must also be specified individually and in a time-varying manner in order to ultimately obtain a flat and thus largely stress-free metal strip. Such an individual, i.e., metal strip- and coil-specific, specification for the distribution of the desired strip tension is made possible by the present invention.

[0015] The required adjustment of the distribution of the target strip tension over time is necessary because both criteria—the distribution of the coil diameter across its width and the thickness distribution of the metal strip across its width—can change over the length of the strip. Thus, they may also change during the winding process.

[0016] The larger the coil diameter becomes during winding, the greater the negative impact of a non-constant distribution of its coil diameter across the coil width and / or a non-constant thickness distribution of the metal strip across its width on the flatness, and the more strongly counteracting measures are required—as claimed—by a suitably predetermined distribution of the desired strip tension. Further advantageous embodiments of the method according to the invention are the subject of the dependent claims.

[0017] The above-mentioned object of the invention is further achieved by the computer program product according to claim 7, a device according to claim 8, and a system according to claim 11. The advantages of these solutions correspond to the advantages previously mentioned with reference to the claimed method.

[0018] The invention is described in more detail below with reference to Figures 1 and 2 in the form of exemplary embodiments.

[0019] Fig. 1 illustrates a system for carrying out or applying the control method according to the invention. The system has a winding-reel device 140 for winding a metal strip 5 into a coil 6. With respect to the running direction R of the metal strip 5, at least one actuator 120, 130 for building up strip tension in the metal strip 5 is arranged upstream of the winding-reel device 140, particularly in its inlet area, relative to the running direction R. A flatness measuring roller 150 is preferably arranged downstream of the winding-reel device 140 for measuring the resulting flatness of the metal strip 5, particularly after it has been unwound from the coil 6.

[0020] The at least one actuator serves to adjust and / or vary a manipulated variable. The manipulated variable can be, for example, the bending, crowning and / or axial displacement of at least one of the work rolls of a hot rolling stand 120 or cold rolling stand 130 arranged upstream of the take-up and reeling device 140. Devices which effect the variation of said manipulated variables are assigned to the stands. These devices are, for example, bending cylinders for adjusting and / or varying the bending of the work rolls of the stand and / or a roll cooling device for adjusting and / or varying the crowning of the work rolls of the stands. The device can also be an axial displacement device for adjusting and / or varying the axial position of the work roll and relative to the housing of the rolling stands and relative to the passing metal strip.

[0021] The stands 120, 130, together with their aforementioned devices for setting and / or varying the control variables, act as the actuators for regulating the distribution of the actual strip tension.

[0022] The invention also relates to a method for controlling the distribution of the actual strip tension of the cold-rolled metal strip 5 when it is wound up into the coil 6 by means of the winding-reel device 140.

[0023] Fig. 2 illustrates the process. It comprises the following steps:

[0024] - Determining the distribution of the actual strip tension over the width of the metal strip 5 when winding the metal strip upstream of the winding-reel device 140 with the aid of a strip tension determination device 10; and

[0025] - Controlling the distribution of the actual strip tension to a predetermined distribution of the target strip tension over the width of the metal strip by suitable variation of at least one control variable.

[0026] During winding of the metal strip 5, the distribution of the desired strip tension across the width of the metal strip is adjusted in an adjustment device 60 during winding, taking into account a changing distribution of the winding diameter W of the coil 6 across its width during winding. For example, the distribution of the desired strip tension is reduced in accordance with the coil diameter increasing during winding. This already achieves a certain improvement in the flatness of the subsequently unwound metal strip. According to the invention, however, the distribution of the desired strip tension across the width of the metal strip during winding in the adjustment device 60 is additionally adjusted to the thickness distribution D of the metal strip across its width. In this way, a significantly improved flatness, in particular of the subsequently unwound metal strip 5, is advantageously achieved.

[0027] The distribution of the desired strip tension, which has been adjusted twice in this way, is then compared in a comparator device 20 with the previously or simultaneously determined distribution of the actual strip tension on the winding-reel device 140. Any strip tension control deviation e determined in this process is fed to a controller 30, which, in accordance with the control deviation e, sets or varies at least one of the above-mentioned manipulated variables and outputs it to the associated actuator 40 in such a way that the determined distribution of the actual strip tension is controlled to the at least twice-adjusted distribution of the desired strip tension, i.e. that the strip tension control deviation e becomes as close to zero as possible. This is done by the actuator 120, 130 controlled in this way influencing the controlled system 50. The controlled system 50 is essentially the system according to Fig. 1.

[0028] To carry out the method according to the invention, knowledge of the thickness distribution D of the metal strip 5 across its width at the location of the winding-reel device 140, preferably at its inlet, is required. However, according to one embodiment of the invention, the thickness distribution of the metal strip 5 can alternatively be determined upstream of the winding-reel device 140, for example in the region of a strand guide 110 upstream of the winding-reel device 140, in the region of the hot rolling stand 120 of a hot rolling mill and / or in the region of the cold rolling stand 130 of an upstream cold rolling mill. Within or at the outlet of the strand guide 110, for example, the profile of a cast strand can be determined, from which the metal strip is later produced. At the inlet, inside or at the outlet of the hot rolling stand 120, for examplethe profile of a hot-rolled metal strand or slab from which the metal strip is later produced is determined.

[0029] If necessary, i.e., in cases where the distance between the location where the thickness distribution is determined and the winding-reel device 140 becomes too large, the thickness distribution determined upstream of the winding-reel device as a representative is converted to the thickness distribution of the metal strip at the level of the inlet of the winding-reel device using a thickness distribution conversion module 160. This distance is considered too large if the difference between the thickness distribution determined upstream and the thickness distribution at the winding-reel device exceeds a specified permissible deviation.

[0030] If the thickness distribution D of the metal strip at the inlet of the winding-reel device 140 can be determined directly, the conversion module 160 is unnecessary.

[0031] The thickness distribution of the metal strip 5 across its width is determined, for example, by manual or automatic measuring.

[0032] List of reference symbols

[0033] 10 Strip tension detection device

[0034] 20 Comparator device

[0035] 30 controllers

[0036] 50 controlled systems

[0037] 100 device

[0038] 110 Strand guide

[0039] 120 hot rolling stand

[0040] 130 cold rolling mill

[0041] 140 Winding-reel device

[0042] 150 Flatness measuring roller

[0043] 160 Thickness distribution conversion module

[0044] D Thickness distribution in width direction of the metal strip e Strip tension control deviation

[0045] R Transport direction of the metal strip

[0046] W Distribution of the winding diameter of the coil over its width

Claims

Patent claims: 1 . A method for controlling the distribution of strip tension when coiling a cold-rolled metal strip (5) into a coil (6) by means of a winding-reel device (140), comprising the following steps: - detecting the distribution of the actual strip tension over the width of the metal strip (5) when winding the metal strip upstream of the winding-reel device (140); and - Controlling the distribution of the actual strip tension to a predetermined distribution of the desired strip tension across the width of the metal strip (5) by suitable variation of at least one manipulated variable; wherein the distribution of the desired strip tension across the width of the metal strip (5) is adapted during the coiling process, taking into account a changing distribution of the winding diameter (W) of the coil (6) across its width during the coiling process; characterized in that the distribution of the desired strip tension across the width of the metal strip (5) is adjusted during coiling, taking into account a thickness distribution (D) of the metal strip across its width.

2. Method according to claim 1, characterized in that the thickness distribution (D) of the metal strip (5) is determined over its width upstream of the winding-reel device (140), for example in the region of an upstream strand guide (110), an upstream hot stand (120), an upstream cold rolling stand (130); and that - if necessary - the determined thickness distribution (D) upstream of the winding-reel device (140) is applied to the thickness distribution of the metal strip at the level of the winding-reel device with the aid of an io Thickness distribution conversion module (160).

3. Method according to one of the preceding claims, characterized in that the resolution of the determined thickness distribution (D) of the metal strip (5) corresponds to the resolution of a flatness measuring roller (150) with which the flatness of the metal strip is determined after it has been removed from the coil (6) has been settled.

4. Method according to one of the preceding claims, characterized in that the distribution of the desired strip tension represents its absolute value in the width direction of the metal strip (5); and that the distribution of the desired strip tension is reduced in amount in accordance with the coil diameter increasing during winding, and vice versa.

5. Method according to one of the preceding claims, characterized in that the thickness distribution (D) of the metal strip (5) across the width is determined by measuring.

6. Method according to one of the preceding claims, characterized in that the manipulated variable is, for example, the bending, crowning and / or axial displacement of at least one work roll of a hot or cold rolling stand (120, 130) arranged upstream of the winding-reel device (140) with respect to the running direction of the metal strip.

7. A computer program product which can be loaded directly into the memory of a digital computer and comprises software code sections with which the steps according to the method according to any one of the preceding claims are carried out when the detected distribution of the actual strip tension over the width of the metal strip and the determined thickness distribution of the metal strip over its width are provided, and when the computer program product is executed on the computer.

8. Device (100) for regulating the distribution of strip tension when coiling a cold-rolled metal strip, comprising: - a strip tension determining device (10) for determining the distribution of the actual strip tension of the metal strip (5) across its width during coiling; - a comparator device (20) for comparing the distribution of the actual strip tension with a predetermined distribution of the desired strip tension of the metal strip in order to determine a strip tension control deviation (e); - a controller (30) for generating a control signal in accordance with the strip tension control deviation (e); and - at least one actuator (120, 130) for setting and / or varying a control variable in accordance with the control signal; characterized by a strip tension adjustment device (60) for adjusting the distribution of the desired strip tension of the metal strip (5) to a changing distribution of the winding diameter (W) of the coil across its width during winding and to a thickness distribution (D) of the metal strip (5) across its width.

9. Device (100) according to claim 8, characterized in that the device and in particular its band tension Adaptation device (60) is designed to carry out the method according to one of claims 1 to 6.

10. Device (100) according to claim 8 or 9, characterized by a thickness distribution conversion module (160) for converting the thickness distribution (D) of the metal strip (5) upstream of the winding-reel device (140) to the thickness distribution of the metal strip (5) at the level of the inlet of the winding-reel device (140).

11. Plant comprising a hot and / or cold rolling stand (120, 130) for rolling a metal strip; a winding-reel device (140) arranged downstream of the hot and / or cold rolling stand in the transport direction (R) of the metal strip (5) for winding the rolled metal strip (5) into a coil (6), characterized by a device (100) for regulating the distribution of the strip tension during the winding of the metal strip (5) according to one of claims 8-10.

12. Plant according to claim 11, characterized by a strand guide (110) arranged upstream of the hot and / or cold rolling stand in the transport direction (R) of the metal strip (5).

13. Plant according to claim 11 or 12, characterized by a flatness measuring roller (150) arranged downstream of the winding-reel device (140) in the transport direction (R).

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