Development of new control strategies for enhanced use of automatic flatness control in cold rolling
New flatness measurement and control systems have been developed for carbon steel cold rolling mills. An internal model control (IMC) and a model predictive control (MPC) have been designed. These two controllers have been implemented and integrated into the automation systems of a four-high four-stand tandem mill and a six-high reversing mill for sheet products (AHS). The results show good flatness performance: a remarkable decrease of flatness errors has been achieved by the new systems compared with the results using current or older systems for all strip dimensions, materials and mill speeds. Moreover, a new predictive PI flatness controller has been designed for four-high temper and tandem mills to compensate for the varying time delays (i.e. transport time between mill and shapemeter) during accelerations/decelerations. This predictive PI controller applied on a four-high tin plate batch tandem mill has decreased by a factor of two the number of coils rejected for bad flatness. Finally, flatness compensation with transverse strip temperature gradients during rolling has been investigated on a tin plate tandem cold mill; it has been shown that mill coiler wedge measurement is a much more robust solution for temperature profile measurement than classic direct scanner. Furthermore, industrial trials of temperature profile compensation in the mill flatness control system have clearly shown the interest of temperature gradient compensation, both for strip flatness in cold mill and improved strip guiding for the downstream continuous annealing line. These results represent a step forward for flatness quality in cold rolling of flat steel strips.
Bibliographic Reference: EUR 23193 EN (2008), 161 pp. Euro: 20
Availability: Katalogue Number: KI-NA-23193-EN-S The paper version can be ordered online and the PDF version downloaded at: http://bookshop.europa.eu
ISBN: ISBN: 978-92-79-08067-8
Record Number: 201010072 / Last updated on: 2010-01-22
Original language: en
Available languages: en