Rolling Mill Leveling Control Using Multi-Stand Torque Data
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Solution Overview
Problem
Existing strip curvature control methods in tandem mills, particularly at high rolling speeds, suffer from reduced accuracy due to variations in left and right screw-down amounts and measurement errors in strip thickness, leading to product quality issues.
Innovation Solution
A leveling control apparatus and method that utilize torque and tension distribution measurements across multiple rolling mill stands, combined with off-center amount calculations, to adjust screw-down amounts progressively, ensuring accurate leveling corrections and maintaining a constant strip wedge ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If screw-down control is performed using measured tension deviations, then strip curvature control is achieved, but measurement errors and width variations reduce control accuracy
Solution Approach 1:
The patent performs screw-down control at rolling mill stands before the tension detection position, using predicted tension deviations calculated from torque distributions measured at multiple stands. This preliminary action allows correction of strip curvature before the actual tension measurement point, compensating for measurement errors and width variations by using earlier, more reliable torque data from upstream stands.
Solution Approach 2:
The patent introduces torque distribution measurements at multiple rolling mill stands as an intermediary parameter to infer tension deviations. Instead of directly using potentially erroneous tension measurements, the system calculates predicted tension deviations from torque distributions measured at several stands, providing a more accurate basis for screw-down control decisions.
2Reliability
If progressive screw-down adjustment is performed from downstream to upstream, then strip curvature is corrected throughout the tandem mill, but control accuracy decreases due to accumulated errors
Solution Approach 1:
The patent implements a feedback mechanism where torque distributions are measured at multiple rolling mill stands and used to calculate predicted tension deviations. The screw-down adjustments at each stand are based on this feedback from downstream torque measurements, allowing progressive correction while maintaining accuracy by continuously referencing actual measured torque data rather than accumulating errors.
Solution Approach 2:
The system performs screw-down adjustments at upstream stands based on predicted tension deviations calculated from downstream torque measurements. This preliminary action at upstream positions, guided by downstream feedback, allows the system to correct strip curvature proactively before errors accumulate through the tandem mill sequence.
3Productivity
If high rolling speed is used to increase productivity, then production efficiency improves, but strip curvature increases due to screw-down differences and thickness variations
Solution Approach 1:
The patent implements continuous torque distribution measurements across multiple rolling mill stands and continuous calculation of predicted tension deviations. This continuous monitoring and adjustment process maintains strip flatness control even at high rolling speeds, preventing the deterioration of strip curvature that would otherwise occur with increased productivity.
Solution Approach 2:
The system uses torque distribution measurements at intermediate rolling mill stands as mediators to detect and correct screw-down differences and thickness variations. These intermediate measurements provide early warning of strip curvature issues, allowing corrective screw-down adjustments to be made before curvature becomes significant, even during high-speed operation.
Data Source
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AI summary
A leveling control apparatus 150 includes a torque acquisition unit 161 that calculates, from torques measured by shapemeters 91, 92, 93, 94, 95, and 96 individually provided between a plurality of rolling stands, a torque distribution applied in a widthwise direction of a steel sheet 1 between each adjacent ones of the plurality of rolling stands, a primary component computing unit 162 that calculates a tension distribution in the widthwise direction from the calculated torque distribution and calculates a primary component in a case where a tension distribution of the steel strip 1 is represented by a polynomial from the tension distribution, a leveling correction amount computing unit 163 that calculates, on the basis of the calculated primary components, a leveling correction amount for a rolling stand immediately preceding on the rolling upstream side among the plurality of rolling stands, and a leveling amount changing unit 164 that changes, on the basis of the calculated leveling correction amounts, the leveling amounts in order toward the rolling upstream side from the (last - 1)th stand among the plurality of rolling stands.