Real-time rule-based control of the thermal crown of work rolls installed in hot strip mills

The extreme thermal conditions suffered by the work rolls of hot strip mills provoke the appearance of nonuniform thermal expansion or thermal crown. The rolling of strips under bad thermal crown conditions generally produces products of unacceptable quality. An adequate cooling system can reduce thermal crown and improve production quality but, due to the complexity of the rolling process itself, and to the impossibility of measuring the thermal crown of the work rolls on-line, the coolant fluxes are rarely modified by the mill operators, thereby reducing cooling effectiveness. This paper presents a novel real-time control system for the thermal crown. It uses a thermal model to estimate the thermal crown of the work rolls and a set of rules that, using the estimated thermal crown and information about the rolling program and the fluxes of coolant, generates adequate set-points for a cooling system.