Hot Rolling Strip Thickness Control for Stable Leading-End Passage
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Solution Overview
Problem
Existing hot rolling mill technologies face challenges in maintaining the finishing temperature and shape of extremely thin hot rolled steel strips, leading to difficulties in passing the leading end due to high-speed rolling and increased equipment costs associated with installing heating devices.
Innovation Solution
A strip thickness control device that measures and adjusts the gap between rolling stands to set a passable strip thickness, allowing the leading end to be passed reliably without the need for additional heating devices, using a strip thickness meter, gap calculating unit, gap setting unit, automatic strip thickness control unit, and target strip thickness changing unit to gradually adjust the strip thickness to the product target thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the strip thickness is reduced to produce extremely thin hot rolled steel strip, then the product thickness is improved, but the finishing temperature decreases significantly and it becomes difficult to pass the leading end
Solution Approach 1:
The patent applies preliminary action by setting a larger gap between rolls at the entry side of the finishing mill before the leading end of the material-to-be-rolled arrives. This preliminary gap adjustment allows the leading end to pass through while maintaining temperature, and then the gap is gradually reduced to the target value during the rolling of the body portion, eliminating the need for heating devices.
2Productivity
If the rolling speed is increased to improve productivity, then the production efficiency is improved, but the leading end cannot be passed due to shape deterioration and warpage
Solution Approach 1:
The patent applies dynamics by making the gap between rolls variable rather than fixed. The gap is dynamically adjusted based on the position of the material-to-be-rolled: a larger gap is set at the entry side to accommodate the leading end, and then the gap is gradually reduced to the target value during the rolling of the body portion. This dynamic adjustment allows high-speed rolling while ensuring reliable passage of the leading end.
3Temperature
If a heating device is installed to maintain the finishing temperature, then the temperature control is improved, but the equipment cost increases
Solution Approach 1:
The patent applies the taking out principle by removing the heating device from the system. Instead of installing expensive heating equipment at the entry side of the finishing mill, the patent achieves temperature maintenance through purely mechanical means - by setting a larger initial gap between rolls that allows the leading end to pass through without excessive deformation and heating, then gradually reducing the gap to the target value.
4Manufacturing precision
If the gap between rolls is set to the target thickness from the beginning, then the manufacturing precision is improved, but the leading end cannot be passed reliably
Solution Approach 1:
The patent applies preliminary action by setting a larger gap between rolls before the leading end arrives, rather than setting the gap to the final target value immediately. This preliminary larger gap allows the leading end to pass through reliably without excessive deformation or temperature drop. After the leading end passes, the gap is gradually reduced to the target value to achieve the desired manufacturing precision for the body portion of the material-to-be-rolled.
Data Source
AI summary
The present disclosure provides a strip thickness control device for a hot rolling mill that can reliably pass a leading end of a material-to-be-rolled without raising equipment cost even in a case of rolling the material-to-be-rolled extremely thinly. The strip thickness control device for a hot rolling mill includes a strip thickness meter installed at a delivery side of a last one of rolling stands in a series direction, a gap calculating unit that calculates a gap between rolls in each of the rolling stands, the gap being larger than a product target strip thickness of the material-to-be-rolled and corresponding to a passable strip thickness that enables a leading end of the material-to-be-rolled to be passed stably, a gap setting unit that sets the gap calculated by the gap calculating unit for each of the rolling stands, an automatic strip thickness control unit that executes automatic strip thickness control of minimizing a strip thickness deviation between a strip thickness measured value of the strip thickness meter and the passable strip thickness, and a target strip thickness changing unit that changes the passable strip thickness to the product target strip thickness by adding a strip thickness bias to the strip thickness deviation at a predetermined ramp rate after the leading end of the material-to-be-rolled is passed through the last one of the rolling stands.