Rolling Mill Roll Gap Control for Thermal Asymmetry
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Solution Overview
Problem
In rolling mills, differential thermal expansion due to asymmetric heat sources and frictional differences between work rolls leads to non-uniform roll gaps, causing strip deviation and production delays, as existing control methods fail to accurately and rapidly correct for these asymmetries.
Innovation Solution
A method involving the measurement of work roll radii at multiple locations to create a longitudinal profile, allowing for tilting of the rolls to minimize gap differences on either side of the centerline, using sensors and hydraulic forces to apply equal and opposite forces to correct the differential gap.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional gap setting methods are used, then the gap can be established, but the differential gap caused by thermal asymmetry cannot be corrected, leading to strip deviation
Solution Approach 1:
The system performs preliminary measurement of the roll gap profile using sensors before rolling operations begin. This allows the control system to pre-calculate and apply the necessary tilting corrections to the work rolls, ensuring uniform gap distribution across the roll length before the strip enters the rolling zone, thereby preventing strip deviation caused by thermal asymmetry.
Solution Approach 2:
The system continuously monitors the actual roll gap profile using measurement sensors positioned around the work rolls. The measured data is fed back to the control system, which compares it against the target uniform gap profile and dynamically adjusts the roll tilting mechanism in real-time to compensate for thermal asymmetry and maintain gap uniformity during rolling operations.
2Reliability
If manual intervention is used to correct strip steering, then cobble can be prevented, but production efficiency decreases due to manual intensity and delay
Solution Approach 1:
The control system automatically monitors strip position and roll gap profile, and self-adjusts the work roll tilting to prevent strip deviation and cobble formation. This automated self-correction eliminates the need for manual intervention, maintaining reliable cobble prevention while significantly improving production efficiency by eliminating manual response delays.
Solution Approach 2:
The system replaces manual mechanical adjustment of roll tilting with an automated control system that uses sensors to detect strip position and differential gap conditions, then automatically actuates the tilting mechanism. This substitution of manual operation with automated sensing and control prevents cobble while maintaining continuous high-speed production.
3Measurement precision
If full zero is performed to establish datum, then gap setting accuracy improves, but time consumption increases
Solution Approach 1:
The system performs the zero establishment and datum setting as a preliminary automated operation before production begins. Sensors automatically measure the roll profiles and establish the reference datum without requiring time-consuming manual procedures, achieving high measurement precision while minimizing the time lost during setup.
Solution Approach 2:
The system replaces manual zero-establishment procedures with automated sensor-based measurement and control system calibration. The sensors automatically detect roll positions and establish the datum reference, eliminating the time-consuming manual operations while maintaining or improving measurement precision through more accurate sensing capabilities.
4Stability of the object's composition
If work rolls are ground with symmetric profile, then initial gap uniformity is achieved, but thermal asymmetry during operation causes differential gap
Solution Approach 1:
The system intentionally introduces asymmetric control adjustments to compensate for the inherent thermal asymmetry that develops during operation. While the rolls are ground with symmetric profiles for initial uniformity, the control system applies differential tilting corrections based on real-time temperature and gap measurements, creating an asymmetric control response that counteracts the thermal asymmetry and maintains gap uniformity under thermal load.
Solution Approach 2:
The system dynamically changes the roll gap parameters during operation by adjusting the tilting angle of the work rolls based on measured temperature distribution and actual gap profile. This allows the system to adapt to thermal asymmetry development, maintaining manufacturing precision despite the changing thermal conditions that cause differential gap expansion.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method effectively reduces and stabilizes the roll gap differences, preventing strip deviation and enabling more precise and rapid adjustments, thereby improving production efficiency and reducing the risk of cobble and trimmer issues.
Implementation Method 1
a first plurality of sensors arranged to measure a radius of the first work roll at a plurality of locations around a circumference of the first work roll
Implementation Method 2
a first hydraulic actuator arranged to apply a first force to a first end of the first work roll and a second hydraulic actuator arranged to apply a second force to a second end of the first work roll
Implementation Method 3
The sources of heat generation and dissipation are not necessarily symmetric about the strip centerline and a temperature difference across the mill can therefore build up. This thermal profile results in asymmetrical roll thermal expansion
Data Source
AI summary
A method of controlling a roll gap between first and second work rolls (102, 104) that includes defining a plurality of work surface locations spaced apart along the first work roll (102) in the longitudinal direction; obtaining a radius of the work surface (102a) of the first work roll (102) at each of the work surface locations; based on the radii of the work surface locations, obtaining a longitudinal profile of the work surface (102a); based on the longitudinal profile, tilting the first work roll (102) relative to the second work roll (104) in the common plane in order to reduce a difference in the average size of the gap either side of a centerline (CL), which bisects the longitudinal axes of the first and second work rolls (102, 104).