Tandem Rolling Mill Tightening Load Control
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Solution Overview
Problem
Existing methods for manufacturing fine-grained steel using tandem rolling mills face challenges in controlling the operation to achieve large reduction rolling without exceeding the tightening load limits, leading to equipment maintenance issues and difficulties in achieving target sheet thicknesses.
Innovation Solution
A method of controlling the operation of a tandem rolling mill by pre-applying a tightening load to specific stands and adjusting the roll gap to manage the sheet thickness, using shape control devices to predict and manage changes in rolling load and shape, ensuring the tightening load remains within safe limits during kiss roll conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If large reduction rolling is carried out in the latter-stage stand to refine crystal grains, then the mechanical properties of the steel sheet are improved, but the tightening load exceeds the upper limit causing equipment breakdown
Solution Approach 1:
The patent applies preliminary action by pre-applying a tightening load to the latter-stage stand before the material is fed into it. This advance preparation allows the rolling mill to withstand the tremendously large kiss roll load that occurs during large reduction rolling without causing equipment breakdown. The tightening load is controlled to be within a specific range that prevents torque circulation and thrust force issues while enabling the necessary large deformation for grain refinement.
Solution Approach 2:
The patent changes the parameter of tightening load from a static or conventional setting to a dynamically controlled parameter that is pre-applied and maintained within a specific range. By controlling the tightening load to be greater than zero and less than or equal to a predetermined upper limit, the system enables large reduction rolling (achieving fine-grained steel) while preventing equipment failure from torque circulation and axial forces during kiss roll conditions.
2Reliability
If the tightening load is limited to prevent equipment breakdown, then the equipment reliability is improved, but the target sheet thickness cannot be achieved
Solution Approach 1:
The patent employs feedback control by monitoring the tightening load and adjusting the roll gap accordingly. The control method determines a roll gap based on the tightening load to ensure that when the material passes through the stand, the target sheet thickness is achieved while the tightening load remains within safe limits. This feedback mechanism allows the system to balance equipment protection with manufacturing precision.
Solution Approach 2:
The patent makes the roll gap dynamic rather than fixed. The roll gap is determined based on the tightening load conditions, allowing the system to adapt the gap setting to maintain both equipment reliability and sheet thickness precision. This dynamic adjustment enables the rolling mill to operate safely during kiss roll conditions while still achieving the required thickness control for fine-grained steel production.
3Manufacturing precision
If a small roll gap is set in advance to achieve target sheet thickness, then the sheet thickness precision is improved, but the tightening load becomes excessively large causing equipment damage
Solution Approach 1:
The patent applies preliminary action by pre-applying a controlled tightening load before the material is fed into the stand. This pre-tightening is done at a level that is sufficient to prevent equipment breakdown during kiss roll but is controlled to remain within safe limits. By preparing the stand in advance with an appropriate tightening load, the system can then achieve target sheet thickness without requiring excessively large forces that would cause equipment damage.
Data Source
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AI summary
The present invention provide: a method of controlling operation of a tandem rolling mill which enables large reduction rolling in the latter-stage stand of the tandem rolling mill that is necessary for manufacturing fine-grained steel and the like; and a method of manufacturing a hot-rolled steel sheet. The method of controlling operation of a tandem rolling mill comprises: a first step of determining a sheet thickness on an exit side of each stand in rolling a constant portion of the material to be rolled; and a second step of determining a sheet thickness on the exit side of each stand in rolling a front end portion of the material to be rolled, such that the pre-tightening load becomes a set value or less; the material to be rolled is rolled to have the exit side sheet thickness determined in the second step, until at least the front ent portion of the material to be rolled is fed into each of the stands; the constant portion of the material to be rolled is rolled by the (N-m+1)-th stand to the N-th stand to have the exit side sheet thickness determined in the first step; and the sheet thicknesses on the exit sides of the (N-m+1)-th stand to the N-th stand determined in the second step are larger than the sheet thicknesses determined in the first step. The method of manufacturing a hot-rolled steel sheet comprises the step of rolling a steel sheet by using a row of hot finishing mills the operation of which is controlled by the above method.