METHOD AND PLANT FOR INTEGRATED MONITORING AND CONTROL OF STRIP FLATNESS AND STRIP PROFILE

Abstract

Apparatus and method of controlling strip geometry in casting strip having a rolling mill. A target thickness profile is calculated as a function of the measured entry thickness profile of the strip while satisfying profile and flatness operating requirements. A differential strain feedback from longitudinal strain in the strip is calculated by a control system by comparing the exit thickness profile with the target thickness profile, and a control signal is generated to control a device capable of affecting the geometry of the strip processed by the hot rolling mill. A feed-forward control reference and/or sensitivity vector may also be calculated as a function of the target thickness profile, and used in generating the control signal sent to the control device. The control device may be selected from one or more of the group consisting of a bending controller, gap controller and coolant controller.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic drawing illustrating a thin strip casting plant having a rolling mill and a control architecture;

FIG. 2 is a block diagram of the control architecture of FIG. 1 interfacing to the rolling mill of FIG. 1;

FIG. 3 is a more detailed block diagram of the control architecture of FIG. 1. and FIG. 2 interfacing to the rolling mill of FIG. 1 and FIG. 2;

FIG. 4 is a flowchart of an embodiment of a method of controlling strip geometry in casting strip having a hot rolling mill;

FIG. 5 is a flowchart of a method of producing thin cast strip with a controlled strip geometry by continuous casting; and

FIG. 6 is a graph illustrating how a sensitivity vector is obtained.

Claims

1. A method of controlling strip geometry in casting strip having a hot rolling mill, said method comprising: measuring an entry thickness profile of an incoming metal strip before the metal strip enters the hot rolling mill;calculating a target thickness profile as a function of the measured entry thickness profile while satisfying profile and flatness operating requirements;measuring an exit thickness profile of the metal strip after the metal strip exits the hot rolling mill;calculating a differential strain feed back from longitudinal strain in the strip by comparing the exit thickness profile with the target thickness profile derived from the measured entry thickness profile; andcontrolling a device capable of affecting the geometry of the strip exiting the hot rolling mill in response to at least said differential strain feed-back.

2. The method of controlling strip geometry in casting strip having a hot rolling mill of claim 1 where the device capable of affecting the geometry of the strip exiting the hot rolling mill is selected from one or more of the group consisting of a bending controller, a gap controller and a coolant controller.

3. The method of controlling strip geometry in casting strip having a hot rolling mill of claim 1 further comprising: calculating a roll gap pressure profile from the entry thickness profile and dimensions and characteristics of the hot rolling mill;calculating a feed-forward control reference and a sensitivity vector as a function of the target thickness profile and the roll gap pressure profile to allow compensation for profile and flatness fluctuations in the cast strip; andfurther controlling the device capable of affecting the geometry of the strip exiting the hot rolling mill in response to said calculated feed-forward control reference and said calculated sensitivity vector.

4. The method of controlling strip geometry in casting strip having a hot rolling mill of claim 1 further comprising: calculating a roll gap pressure profile from the entry thickness profile and dimensions and characteristics of the hot rolling mill;calculating a feed-forward control reference as a function of the target thickness profile and the roll gap pressure profile to allow compensation for profile and flatness fluctuations in the cast strip; andfurther controlling the device capable of affecting the geometry of the strip exiting the hot rolling mill in response to said calculated feed-forward control reference.

5. The method of controlling strip geometry in casting strip having a hot rolling mill of claim 1 further comprising further comprising: calculating a roll gap pressure profile from the entry thickness profile and dimensions and characteristics of the hot rolling mill;calculating a sensitivity vector as a function of the target thickness profile and the roll gap pressure profile to allow compensation for profile and flatness fluctuations in the cast strip; andfurther controlling the device capable of affecting the geometry of the strip exiting the hot rolling mill in response to said calculated sensitivity vector.

6. The method of controlling strip geometry in casting strip having a hot rolling mill of claim 3 further comprising generating an adaptive roll gap error vector from the measured exit thickness profile and using the adaptive roll gap error vector in calculating at least one of the feed-forward control reference and the sensitivity vector.

7. The method of controlling strip geometry in casting strip having a hot rolling mill of claim 1 where calculating said target thickness profile includes performing at least one of time filtering and spatial frequency filtering.

8. The method of controlling strip geometry in casting strip having a hot rolling mill of claim 2 where said controlling step includes performing symmetric feed-back control and asymmetric feed-back control of the bending controller and the gap controller.

9. The method of controlling strip geometry in casting strip having a hot rolling mill of claim 1 where said controlling step includes subtracting out systematic errors from said differential strain feed back when the rolling mill is engaged, said systematic errors being generated through comparison of the entry and exit thickness profiles when the rolling mill is disengaged.

10. The method of controlling strip geometry in casting strip having a hot rolling mill of claim 1 where said controlling step includes performing temperature compensation and buckle detection.

11. The method of controlling strip geometry in casting strip having a hot rolling mill of claim 1 where said controlling step includes performing at least one of operator-induced coolant trimming and operator-induced bending trimming.

12. The method of controlling strip geometry in casting strip having a hot rolling mill of claim 1 where said target thickness profile inhibits strip buckling.

13. A control architecture for controlling strip geometry in casting strip having a hot rolling mill, said control architecture comprising: an entry gauge apparatus capable of measuring an entry thickness profile of an incoming metal strip before said metal strip enters said rolling mill;a target thickness profile model capable of calculating a target thickness profile as a function of said measured entry thickness profile while satisfying profile and flatness operating requirements;an exit gauge apparatus capable of measuring an exit thickness profile of said metal strip after said metal strip exits said rolling mill;a differential strain feed back model capable of calculating a differential strain feed-back from longitudinal strain in the strip by comparing the exit thickness profile with the target thickness profile derived from the measured entry thickness profile; anda control model capable of controlling a device capable of affecting the geometry of the strip exiting the hot rolling mill in response to at least said differential strain feed back.

14. The control architecture for controlling strip geometry in casting strip having a hot rolling mill of claim 13 where the device capable of affecting the geometry of the strip exiting the hot rolling mill is selected from one or more of the group consisting of a bending controllers a gap controller, and a coolant controller.

15. The control architecture for controlling strip geometry in casting strip having a hot rolling mill of claim 13 further comprising: a roll-gap model capable of calculating a roll gap pressure profile from the entry thickness profile and dimensions and characteristics of the hot rolling mill; anda feed-forward roll stack deflection model capable of calculating a feed-forward control reference and a sensitivity vector as a function of the target thickness profile and the roll gap pressure profile to allow compensation for profile and flatness fluctuations in the cast strip.

16. The control architecture for controlling strip geometry in casting strip having a hot rolling mill of claim 13 further comprising: a roll-gap model capable of calculating a roll gap pressure profile from the entry thickness profile and dimensions and characteristics of the hot rolling mill; anda feed-forward roll stack deflection model capable of calculating a feed-forward control reference as a function of the target thickness profile and the roll gap pressure profile to allow compensation for profile and flatness fluctuations in the cast strip.

17. The control architecture for controlling strip geometry in casting strip having a hot rolling mill of claim 13 further comprising: a roll-gap model capable of calculating a roll gap pressure profile from the entry thickness profile and dimensions and characteristics of the hot rolling mill; anda feed-forward roll stack deflection model capable of calculating a sensitivity vector as a function of the target thickness profile and the roll gap pressure profile to allow compensation for profile and flatness fluctuations in the cast strip.

18. The control architecture for controlling strip geometry in casting strip having a hot rolling mill of claim 15 further comprising an adaptive roll stack deflection model capable of generating an adaptive roll gap error vector from the measured exit thickness profile and using the adaptive roll gap error vector in calculating at least one of the feed-forward control reference and the sensitivity vector.

19. The control architecture for controlling strip geometry in casting strip having a hot rolling mill of claim 13 where said target thickness profile model further includes at least one of time filtering capability and spatial frequency filtering capability as part of calculating said target thickness profile.

20. The control architecture for controlling strip geometry in casting strip having a hot rolling mill of claim 14 where said control model includes a symmetric feed back capability and an asymmetric feed back capability for controlling the bending controller and the gap controller.

21. The control architecture for controlling strip geometry in casting strip having a hot rolling mill of claim 113 where said differential strain feed back model includes an automatic nulling capability capable of subtracting out systematic errors from said differential strain feed back when the rolling mill is engaged, said systematic errors being generated through comparison of the entry and exit thickness profiles when the rolling mill is disengaged.

22. The control architecture for controlling strip geometry in casting strip having a hot rolling mill of claim 13 where said differential strain feed back model includes temperature compensation capability and buckle detection capability.

23. The control architecture for controlling strip geometry in casting strip having a hot rolling mill of claim 13 where said control architecture supports at least one of operator-induced coolant trimming and operator-induced bending trimming.

24. The control architecture for controlling strip geometry in casting strip having a hot rolling mill of claim 13 where said target thickness profile model inhibits strip buckling.

25. A method of producing thin cast strip with a controlled strip geometry by continuous casting, said method comprising: (a) assembling a thin strip caster having a pair of casting rolls having a nip therebetween;(b) assembling a metal delivery system capable of forming a casting pool between the casting rolls above the nip with side dams adjacent the ends of the nip to confine said casting pool;(c) assembling, adjacent the thin strip caster, a hot rolling mill having work rolls with work surfaces forming a roll gap between them through which incoming hot strip is rolled, said work rolls having work roll surfaces relating to a desired shape across the work rolls;(d) assembling a device capable of affecting the geometry of said strip exiting said hot rolling mill in response to control signals;(e) assembling a control system capable of calculating a differential strain feed-back from longitudinal strain in the strip by comparing an exit thickness profile with a target thickness profile derived from a measured entry thickness profile and generating control signals in response to at least said calculated differential strain feed-back; and(f) connecting said control system to said device capable of affecting the geometry of said strip exiting said hot rolling mill in response to said generated control signals from the control system.

26. The method of producing thin cast strip with a controlled strip geometry by continuous casting of claim 25 where said device capable of affecting the geometry of said strip exiting said hot rolling mill is selected from one or more of the group consisting of a bending controller, a gap controller, and a coolant controller.

27. The method of producing thin cast strip with a controlled strip geometry by continuous casting of claim 25 where said control system is further capable of calculating a feed-forward control reference and a sensitivity vector, and further capable of generating control signals in response said differential strain feed back, said feed-forward control reference, and said sensitivity vector.

28. The method of producing thin cast strip with a controlled strip geometry by continuous casting of claim 25 where said control system is further capable of calculating a feed-forward control reference, and further capable of generating control signals in response said differential strain feed back and said feed-forward control reference.

29. The method of producing thin cast strip with a controlled strip geometry by continuous casting of claim 25 where said control system is further capable of calculating a sensitivity vector, and further capable of generating control signals in response said differential strain feed back and said sensitivity vector.

30. The method of producing thin cast strip with a controlled strip geometry by continuous casting of claim 27 where said feed-forward control reference and said sensitivity vector are calculated as a function a target thickness profile, derived from a measured entry thickness profile, and a roll gap pressure profile to allow compensation for profile and flatness fluctuations in the cast strip.

31. A thin cast strip plant for producing thin cast strip with a controlled strip geometry by continuous casting, said thin cast strip plant comprising: (a) a thin strip caster having a pair of casting rolls having a nip therebetween;(b) a metal delivery system capable of forming a casting pool between the casting rolls above the nip with side dams adjacent the ends of the nip to confine said casting pool;(c) a drive capable of counter-rotating the casting rolls to form solidified metal shells on the surfaces of the casting rolls and cast thin steel strip through the nip between the casting rolls from the solidified shells;(d) a hot rolling mill having work rolls with work surfaces forming a roll gap therebetween through which cast strip from the thin strip caster may be rolled;(e) a device connected to said hot rolling mill capable of affecting the geometry of strip processed by the hot rolling mill in response to control signals; and(f) a control system capable of calculating a differential strain feed-back from longitudinal strain in the strip by comparing a exit thickness profile with a target thickness profile derived from a measured entry thickness profile, capable of generating control signals in response said differential strain feed-back, and connected to said device to cause the device to affect the geometry of strip processed by the hot rolling mill in response to said control signals.

32. The thin cast strip plant for producing thin cast strip with a controlled strip geometry by continuous casting of claim 31 where said device capable of affecting the geometry of said strip processed by the hot rolling mill is selected from one or more of the group consisting of a bending controller, a gap controller, and a coolant controller.

33. The thin cast strip plant for producing thin cast strip with a controlled strip geometry by continuous casting of claim 31 where said control system is further capable of calculating a feed-forward control reference and a sensitivity vector, and further capable of generating control signals in response said feed-forward control reference and said sensitivity vector to cause said device to affect the geometry of strip processed by the hot rolling mill in response to said control signals.

34. The thin cast strip plant for producing thin cast strip with a controlled strip geometry by continuous casting of claim 31 where said control system is further capable of calculating a feed-forward control reference, and further capable of generating control signals in response said feed-forward control reference to cause said device to affect the geometry of strip processed by the hot rolling mill in response to said control signals.

35. The thin cast strip plant for producing thin cast strip with a controlled strip geometry by continuous casting of claim 31 where said control system is further capable of calculating a sensitivity vector, and further capable of generating control signals in response said sensitivity vector to cause said device to affect the geometry of strip processed by the hot rolling mill in response to said control signals.

36. The thin cast strip plant for producing thin cast strip with a controlled strip geometry by continuous casting of claim 33 where said feed-forward control reference and said sensitivity vector are calculated as a function a target thickness profile, derived from a measured entry thickness profile, and a roll gap pressure profile to allow compensation for profile and flatness fluctuations in the cast strip.