Strip Flatness Control via Hot Rolling Thickness Profile Targeting
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Solution Overview
Problem
Current flatness control methods in rolled material production lines often result in flatness errors and the risk of strip break due to mismatched roll gaps and thickness profiles between hot and cold rolling mills, leading to inefficiencies and reduced yield.
Innovation Solution
A method that determines a thickness profile target for the hot rolling mill based on flatness data from cold rolling mills, allowing for adjustments that match the incoming thickness profile and reduce flatness errors, using mechanical actuators to adjust roll gaps and thermal actuators for local corrections, with machine learning or statistical techniques for optimization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the roll gap of cold rolling mill is controlled according to flatness target, then flatness control is improved, but the required flatness compensation may exceed acceptable operating conditions or cause strip break
Solution Approach 1:
The patent applies preliminary action by determining an achievable flatness target before the cold rolling process based on the thickness profile. This pre-determined target ensures that the required flatness compensation remains within the acceptable operating conditions of the cold rolling mill, preventing strip break while still achieving good flatness control.
Solution Approach 2:
The patent changes the parameter approach by shifting from controlling roll gap directly to controlling the thickness profile in the hot rolling mill. By adjusting the thickness profile parameters to match the roll gap of the cold rolling mill, the system achieves flatness control without exceeding mechanical actuator limits.
2Manufacturing precision
If mechanical actuators are used to adjust roll gap in cold rolling mill, then flatness correction capability is improved, but the actuators may not allow the roll gap to be formed according to the thickness profile
Solution Approach 1:
The patent applies inversion by reversing the control approach: instead of adjusting the cold rolling mill's roll gap to match the thickness profile, it adjusts the thickness profile in the hot rolling mill to match the cold rolling mill's roll gap. This resolves the limitation of mechanical actuators by working within their fixed capabilities.
Solution Approach 2:
The system performs preliminary determination of the achievable flatness target based on the cold rolling mill's roll gap characteristics before the material enters the cold rolling mill. This ensures that the thickness profile is pre-adjusted to be compatible with the mechanical actuator limitations.
3Adaptability or versatility
If multiple cold rolling mills with different roll gaps are used, then production flexibility is improved, but flatness errors increase due to mismatched roll gaps and thickness profiles
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the thickness profile parameters based on the specific roll gap of each cold rolling mill. When material transfers between mills with different roll gaps, the thickness profile is re-determined to match the new mill's characteristics, maintaining flatness accuracy across multiple mills.
Solution Approach 2:
Before each cold rolling pass through different mills, the system preliminarily determines the achievable flatness target specific to that mill's roll gap. This ensures that the thickness profile is optimized for each specific mill configuration, preventing flatness errors even when using multiple mills with different parameters.
Data Source
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AI summary
A method of controlling flatness of a strip (16) of rolled material in a production line (10) comprising a hot rolling mill (12) and at least one cold rolling mill (14), downstream of the hot rolling mill (12), the method comprising determining flatness data of the strip (16) in one or more of the at least one cold rolling mill (14) and/or following passing of the strip (16) through one or more of the at least one cold rolling mill (14); determining a thickness profile target (50) of the strip (16) for the hot rolling mill (12) based on the flatness data; and passing the strip (16) through the hot rolling mill (12) and adjusting the thickness of the strip (16) based on the thickness profile target (50). A control system (38) and a production line (10) are also provided.