Method Of Controlling Flatness Of Strip Of Rolled Material, Control System And Production Line

Abstract

A method of controlling flatness of a strip of rolled material in a production line including a hot rolling mill and at least one cold rolling mill, downstream of the hot rolling mill, the method including determining flatness data of the strip in one or more of the at least one cold rolling mill and/or following passing of the strip through one or more of the at least one cold rolling mill; determining a thickness profile target of the strip for the hot rolling mill based on the flatness data; and passing the strip through the hot rolling mill and adjusting the thickness of the strip based on the thickness profile target. A control system and a production line are also provided.

Claims

1. A method of controlling flatness of a strip of rolled material in a production line comprising a hot rolling mill and at least one cold rolling mill, downstream of the hot rolling mill, the method comprising: determining flatness data associated with the strip in one or more of the at least one cold rolling mill and/or following passing of the strip through one or more of the at least one cold rolling mill; determining a thickness profile target of the strip for the hot rolling mill based on the flatness data; and passing the strip through the hot rolling mill and adjusting the thickness of the strip based on the thickness profile target.

2. The method according to claim 1, wherein each cold rolling mill comprises at least one mechanical actuator arranged to control one or more rolls of the cold rolling mill, and wherein the flatness data comprises a flatness model associated with one of the at least one mechanical actuator, the flatness model defining an effect on the strip by the mechanical actuator.

3. The method according to claim 2, wherein the production line comprises a plurality of cold rolling mills, wherein the flatness data comprises a flatness model associated with each of one or more of the at least one mechanical actuator for a plurality of cold rolling mills, and wherein the determination of the thickness profile target includes determining a thickness profile target of the strip for the hot rolling mill that best matches a combination of the flatness models.

4. The method according to claim 2, wherein the production line comprises a plurality of cold rolling mills, and wherein the flatness data comprises a flatness model associated with one or more of the at least one mechanical actuator of the most downstream cold rolling mill.

5. The method according to claim 4, wherein the thickness profile target is determined to mirror the flatness model associated with each of one or more of the at least one mechanical actuator of the most downstream cold rolling mill.

6. The method according to claim 2, wherein the flatness model is dependent on a width of the strip.

7. The method according to claim 1, wherein the flatness data comprises a measured flatness of the strip.

8. The method according to claim 7, wherein the flatness data comprises a measured flatness of the strip after passing through a subsequent process with respect to each of the at least one cold rolling mill.

9. The method according to claim 1, wherein the flatness data is determined by means of one or more shape meters.

10. The method according to claim 1, wherein the thickness profile target is determined based on a width of the strip.

11. A control system for controlling flatness of a strip of rolled material in a production line including a hot rolling mill and at least one cold rolling mill, downstream of the hot rolling mill, the control system comprising at least one data processing device and at least one memory having at least one computer program stored thereon, the at least one computer program including program code which, when executed by one or more of the at least one data processing device, causes one or more of the at least one data processing device to perform the steps of: determining flatness data associated with the strip in one or more of the at least one cold rolling and/or following passing of the strip through one or more of the at least one cold rolling mill; determining a thickness profile target of the strip for the hot rolling mill based on the flatness data; and controlling a thickness adjustment of the strip based on the thickness profile target when passing the strip through the hot rolling mill.

12. A production line comprising a hot rolling mill, at least one cold rolling mill, downstream of the hot rolling mill, and a control system to perform the steps of: determining flatness data associated with the strip in one or more of the at least one cold rolling mill and/or following passing of the strip through one or more of the at least one coid roiling mill; determining a thickness profile target of the strip for the hot rolling mill based on the flatness data; and controlling a thickness adjustment of the strip based on the thickness profile target when passing the strip through the hot rolling mill.

13. The method according to claim 3, wherein the production line comprises a plurality of cold rolling mills, and wherein the flatness data comprises a flatness model associated with one or more of the at least one mechanical actuator of the most downstream cold rolling mill.

14. The method according to claim 3, wherein the flatness model is dependent on a width of the strip.

15. The method according to claim 2, wherein the flatness data comprises a measured flatness of the strip.

16. The method according to claim 2, wherein the flatness data is determined by means of one or more shape meters.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Further details, advantages and aspects of the present disclosure will become apparent from the following embodiments taken in conjunction with the drawings, wherein:

[0047] FIG. 1: schematically represents a production line; and

[0048] FIG. 2: schematically represents a typical flatness model and a typical thickness profile target.

DETAILED DESCRIPTION

[0049] In the following, a method of controlling flatness of a strip of rolled material in a production line, a control system for controlling flatness of a strip of rolled material in a production line, and a production line comprising a control system, will be described. The same or similar reference numerals will be used to denote the same or similar structural features.

[0050] FIG. 1 schematically represents a production line 10. The production line 10 comprises a plurality of hot rolling mills 12 and a plurality of cold rolling mills 14. The cold rolling mills 14 are arranged downstream of the hot rolling mills 12. In the example in FIG. 1, the production line 10 comprises two hot rolling mills 12 and five cold rolling mills 14. The production line 10 thus comprises a hot rolling side comprising the hot rolling mills 12 and a cold rolling side comprising the cold rolling mills 14.

[0051] FIG. 1 further shows a strip 16 of rolled material, for example aluminium. In FIG. 1, the strip 16 is conveyed to the right through each hot rolling mill 12 and through each cold rolling mill 14. In this example, the hot rolling mills 12 and the cold rolling mills 14 are each composed in a multi stand tandem mill. In the first hot rolling mill 12, the strip 16 is a slab that is squeezed between rolls such that the thickness is reduced.

[0052] The production line 10 of this example further comprises a plurality of thickness profile measurement devices 18. However, the production line 10 may alternatively comprise only one thickness profile measurement device 18 downstream of the last hot rolling mill 12. Each thickness profile measurement device 18 is configured to measure a thickness profile of the strip 16. In the example in FIG. 1, one thickness profile measurement device 18 is arranged upstream of the most upstream hot rolling mill 12, one thickness profile measurement device 18 is arranged downstream of the most downstream hot rolling mill 12, and one thickness profile measurement device 18 is arranged between each pair of adjacent hot rolling mills 12.

[0053] Each hot rolling mill 12 comprises a plurality of rolls 20 and one or more mechanical actuators 22 for controlling the rolls 20. Similarly, each cold rolling mill 14 comprises a plurality of rolls 24 and one or more mechanical actuators 26 for controlling the rolls 24. Each hot rolling mill 12 and each cold rolling mill 14 also comprises thermal actuators (not illustrated).

[0054] Each hot rolling mill 12 is configured to modify a thickness profile of the strip 16 by means of its mechanical actuators 22. To this end, each hot rolling mill 12 is controlled based on a thickness profile target. The thickness profile target indicates a change in thickness over the width of the strip 16 through the hot rolling mill 12.

[0055] Each cold rolling mill 14 is configured to modify a flatness of the strip 16 by means of its mechanical actuators 26. To this end, each cold rolling mill 14 is controlled by means of one or more flatness models. Each flatness model defines a flatness effect on the strip 16 caused by one of the mechanical actuators 26.

[0056] The production line 10 of this specific example further comprises a coiler 28, an uncoiler 30 and a galvanization or aluminizing station 32. Each of the coiler 28, the uncoiler 30 and the galvanization or aluminizing station 32 constitutes an example of a subsequent process with respect to each of the cold rolling mills 14. The production line 10 of this specific example further comprises a cleaning and pickling station 34 between the hot rolling side and the cold rolling side.

[0057] The production line 10 further comprises a plurality of shape meters 36. Each shape meter 36 is configured to measure a flatness of the strip 16. In the example in FIG. 1, one shape meter 36 is arranged upstream of the most upstream cold rolling mill 14, one shape meter 36 is arranged downstream of the last cold rolling mill 14, and one shape meter 36 is arranged between each pair of adjacent cold rolling mills 14. One shape meter 36 is also arranged downstream of the uncoiler 30, i.e. between the uncoiler 30 and the galvanization or aluminizing station 32.

[0058] The production line 10 further comprises a control system 38. The control system 38 comprises at least one data processing device 40 and at least one memory 42. In FIG. 1, the control system 38 is illustrated as comprising two data processing devices 40 and two memories 42. The at least one memory 42 comprises program code which, when executed by one or more of the at least one data processing device 40, causes one or more of the at least one data processing devices 40 to perform, or command performance of, various steps as described herein.

[0059] In this specific example, the control system 38 comprises a thickness profile controller 44 and a flatness controller 46. Each of the thickness profile controller 44 and the flatness controller 46 comprises a data processing device 40 and a memory 42. The control system 38 for controlling the production line 10 may however be implemented in different ways.

[0060] The flatness controller 46 controls the cold rolling mills 14 to minimize flatness errors based on signals received from the cold rolling mills 14 and/or from the shape meters 36. The thickness profile controller 44 controls the hot rolling mills 12 to minimize thickness profile errors based on signals received from the hot rolling mills 12 and/or the thickness profile measurement devices 18, and from the flatness controller 46.

[0061] The deformation of the thickness profile of the strip 16 induced by rolling depends on several factors, such as temperature of the strip 16, aspect ratio of the strip 16, i.e. width divided by thickness, and the ratio coefficient of friction to strip entry thickness. The predominant factor is the aspect ratio of the strip 16. If the aspect ratio is greater than 3o, deformation of the strip 16 is essentially plane strain, i.e. the strip 16 is reduced in thickness and increased in length with little or no change in width. In cold rolling, especially when rolling thin strips 16, the aspect ratio is typically much higher than 30. In hot rolling on the other hand, the aspect ratio is typically less than 30, particularly for the most upstream hot rolling mill(s) 12, and thus a profile deformation of the strip 16 occurs with a significant increase in width of the strip 16.

[0062] The ability to change the thickness profile of the strip 16 decreases as the aspect ratio increases. Conversely, the ability to correct shape defects of the strip 16 increases and is greatest at the final or most downstream cold rolling mill 14.

[0063] In cold rolling, the thickness profile of the strip 16 and the flatness of the strip 16 are associated. This means that there will be less or no flatness defects in cold rolling if one can provide a roll gap to mirror the incoming thickness profile of the strip 16, i.e. equal elongation transverse the strip 16. The thickness profile of the strip 16 is mainly established in the hot rolling side. Downstream of the hot rolling side, the strip 16 is too cold and too thin compared to its width to be able to change its thickness profile without causing shape issues. It is therefore difficult or impossible to change the thickness profile of the strip 16 in the cold rolling side without causing flatness problems.

[0064] FIG. 2 schematically represents an example of a typical flatness model 48 and a typical thickness profile target 5o. The flatness model 48 is a combination of a second order polynomial and a fourth order polynomial. A flatness model 48 of a mechanical actuator 26 is one example of flatness data associated with the strip 16 in a cold rolling mill 14. A plurality of flatness models 48 may be determined for one mechanical actuator 26. In particular, one or more flatness models 48 may be determined for mechanical actuators 26 of the most downstream cold rolling mill 14.

[0065] The thickness profile target 50 in FIG. 2 is a second order polynomial. The thickness profile target 50 is 1% thicker at the center of the strip 16. The thickness profile target 50 in FIG. 2 thus has a 1% crown.

[0066] As shown in FIG. 2, there is a discrepancy between the thickness profile target 5o and the flatness model 48. This discrepancy cause difficulties for the cold rolling mill 14 to maintain the incoming thickness profile in the roll bite and thus achieve good flatness.

[0067] By making the thickness profile target 50 more closely conform to the flatness model 48, the mechanical actuator 26 of the cold rolling mill 14 can better address flatness errors by means of its roll gap. To this end, the flatness controller 46 is further configured to determine one or more flatness models 48 for one or more mechanical actuators 26. The thickness profile controller 44 may receive one or more flatness models 48 from the flatness controller 46 and determine a thickness profile target 50 for the one or more hot rolling mills 12 based on a combination of the flatness models 48. The thickness profile target determined in this way is not limited to a polynomial or a combination of polynomials, but can be expressed in alternative ways. The thickness profile target 50 can for example be determined by means of machine learning using one or more flatness models 48, one or more measured flatnesses (e.g. a flatness measured immediately downstream of the last cold rolling mill 14) and the thickness profile target 50 as training data.

[0068] The thickness profile target 5o is based on one or more flatness models 48 that can actually be achieved by the respective mechanical actuator 26. Therefore, the mechanical actuators 26 of the cold rolling mills 14 can match the thickness profile from the hot rolling mills 12 to reduce flatness errors.

[0069] Even if a good flatness is obtained in the most downstream cold rolling mill 14, this flatness may change in subsequent processes, for example when the strip 16 is subjected to coiling and uncoiling. This change may for example depend on cooling effects and where in the coil a particular section of the strip 16 is positioned. The thickness profile target 50 may therefore be determined based on a measured flatness of the strip 16 after passing through any of the subsequent processes 28, 30, 32. Also a measured flatness of the strip 16 constitutes an example of flatness data. As shown in FIG. 1, a flatness of the strip 16 is measured immediately upstream of the coiler 28 and immediately downstream of the uncoiler 30. A flatness effect by the coiling and uncoiling can then be determined based on difference between these measured flatnesses. By determining the thickness profile target 50 based on the flatness effect from the coiling and uncoiling, the strip 16 can be made more flat after uncoiling. Moreover, since the flatness effect from coiling and uncoiling is addressed in the hot rolling side and not in the cold rolling side, the risk for strip break is reduced.

[0070] While the present disclosure has been described with reference to exemplary embodiments, it will be appreciated that the present invention is not limited to what has been described above. For example, it will be appreciated that the dimensions of the parts may be varied as needed. Accordingly, it is intended that the present invention may be limited only by the scope of the claims appended hereto.