Systems and methods for controlling flatness of a metal substrate with low pressure rolling
A flatness control system includes a work stand of a finishing line, a plurality of actuators, a flatness measuring device, and a controller. The work stand includes a pair of vertically aligned work rolls. A first work roll of the pair of work rolls includes a plurality of flatness control zones configured to apply a localized pressure to a corresponding region on a substrate. Each actuator corresponds with a one of the plurality of flatness control zones. The flatness measuring device is configured to measure an actual flatness profile of the substrate. The controller is configured to adjust the plurality of actuators such that the localized pressures modify the actual flatness profile to achieve the desired flatness profile at the exit of the stand. The thickness and a length of the substrate remain substantially constant when the substrate exits the work stand.
1. A method of controlling flatness of a substrate, the method comprising:
directing the substrate to a work stand of a finishing line and between a pair of vertically aligned work rolls of the work stand;
applying, by a first work roll of the pair of vertically aligned work rolls, a plurality of localized pressures to the substrate across a width of the substrate, wherein each of the plurality of localized pressures is applied by a corresponding flatness control zone of the first work roll, and wherein the localized pressure applied by each flatness control zone is controlled by a corresponding actuator, wherein the actuators comprise at least an edge actuator for controlling an edge region of the substrate and at least a non-edge actuator for controlling a non-edge region of the substrate, wherein at least one physical characteristic of the edge actuator is different from the non-edge actuator and causes a different localized pressure compared to the localized pressure of the non-edge actuator;
measuring an actual flatness profile of the substrate with a flatness measuring device;
comparing, by a controller, the actual flatness profile with a desired flatness profile; and
adjusting, by the controller, each of the actuators independently from one another such that the plurality of localized pressures modify the actual flatness profile of the substrate to achieve the desired flatness profile while an overall thickness and a length of the substrate remains substantially constant as the substrate enters and exits the work stand so that the overall thickness of the substrate is reduced from 0.0% to 1.0% and so that the work roll pressures applied to the substrate by the work rolls cause the length of the substrate to increase between 0.0% and 1.0%, wherein adjusting each actuator comprises adjusting each actuator to control each corresponding flatness control zone to apply the corresponding localized pressure that, for each flatness control zone, causes a localized elongation of a corresponding portion of the substrate, and
wherein the first work roll comprises an outer surface, and wherein applying the plurality of localized pressures comprises contacting the outer surface of the first work roll with a surface of the substrate.
2. The method of claim 1 , wherein an average of the plurality of localized pressures applied by the first work roll to the substrate is less than a yield strength of the substrate.
3. The method of claim 1 , wherein adjusting the actuators comprises adjusting at least one actuator such that the localized pressure at the flatness control zone corresponding to the at least one actuator is greater than a yield strength of the substrate.
4. The method of claim 3 , wherein adjusting the actuators comprises adjusting a different actuator than the at least one actuator such that the localized pressure at the flatness control zone corresponding to the different actuator is less than the yield strength of the substrate.
5. The method of claim 1 , wherein applying the plurality of localized pressures to the substrate with the first work roll comprises freezing a vertical position of a second work roll vertically aligned with the first work roll.
6. The method of claim 1 , wherein the outer surface of the first work roll is smooth, and wherein adjusting the actuators such that the actual flatness profile achieves the desired flatness profile further comprises smoothing a surface topography of the surface of the substrate.
7. The method of claim 1 , wherein the outer surface of the first work roll comprises a texture, and wherein adjusting the actuators such that the actual flatness profile achieves the desired flatness profile further comprises applying the texture to the surface of the substrate.
8. The method of claim 1 , wherein measuring the actual flatness profile comprises determining regions on the substrate with tensile residual stress and regions on the substrate with compressive residual stress, and wherein adjusting the actuators comprises increasing the localized pressures of flatness control zones corresponding to the regions of tensile residual stress.
9. The method of claim 8 , wherein increasing the localized pressures of flatness control zones corresponding to the regions of tensile residual stress comprises applying localized pressures that cause a localized elongation of from greater than 0.0% to 1.0%.
10. A flatness control system comprising:
a work stand of a finishing line comprising a pair of vertically aligned work rolls, wherein a first work roll of the pair of vertically aligned work rolls comprises a plurality of flatness control zones across a width of the first work roll, and wherein each flatness control zone is configured to apply a localized pressure to a corresponding region on a substrate, wherein the first work roll comprises an outer surface that is configured to contact a substrate during processing;
a plurality of actuators, wherein each actuator corresponds with one of the plurality of flatness control zones and is configured to cause the corresponding flatness control zone to apply the localized pressure to the corresponding region on the substrate by contacting the outer surface of the first work roll with the surface of the substrate, and wherein each actuator is independently controlled, wherein the plurality of actuators comprises at least an edge actuator for controlling an edge region of the substrate and at least a non-edge actuator for controlling a non-edge region of the substrate, wherein at least one physical characteristic of the edge actuator is different from the non-edge actuator and causing a different localized pressure compared to the localized pressure of the non-edge actuator;
a flatness measuring device configured to measure an actual flatness profile of the substrate; and
a controller configured to adjust each actuator of the plurality of actuators independently from one another such that the localized pressures modify the actual flatness profile to achieve a desired flatness profile while an overall thickness and a length of the substrate remains substantially constant when the substrate exits the work stand and such that the localized pressures cause a localized elongation of a plurality of portions of the substrate so that the overall thickness of the substrate is reduced from 0.0% to 1.0% and so that the work roll pressures applied to the substrate by the work rolls cause the length of the substrate to increase between 0.0% and 1.0%, each portion of the substrate corresponding to a particular flatness control zone of the plurality of flatness control zones.
11. The flatness control system of claim 10 , wherein an average of the localized pressures applied by the first work roll to the substrate is less than a yield strength of the substrate.
12. The flatness control system of claim 10 , wherein the controller is configured to adjust at least one actuator such that the localized pressure at the flatness control zone corresponding to the at least one actuator is greater than a yield strength of the substrate.
13. The flatness control system of claim 12 , wherein the controller is configured to adjust a different actuator than the at least one actuator such that the localized pressure at the flatness control zone corresponding to the different actuator is less than the yield strength of the substrate.
14. The flatness control system of claim 10 , wherein the controller is configured to minimize a difference in load between flatness control zones.
15. The flatness control system of claim 10 , wherein the outer surface of the first work roll is smooth having a surface roughness of 0.4-0.6 μm, and wherein the first work roll is configured to smooth a surface topography of the surface of the substrate.
16. The flatness control system of claim 10 , wherein the outer surface of the first work roll comprises a texture, and wherein the first work roll is configured to apply the texture to the surface of the substrate.
17. The flatness control system of claim 10 , wherein the flatness measuring device is configured to determine regions on the substrate with tensile residual stress and regions on the substrate with compressive residual stress, and wherein the controller is configured to adjust the actuators to increase the localized pressures of flatness control zones corresponding to the regions of tensile residual stress.
18. The method of claim 1 , wherein the at least one physical characteristic comprises at least one of a crown of the edge actuator, a diameter of the edge actuator, or a width of the edge actuator.
19. The flatness control system of claim 10 , wherein the at least one physical characteristic comprises at least one of a crown of the edge actuator, a diameter of the edge actuator, or a width of the edge actuator.