Adapted process control and measuring techniques for hot strip geometry optimisation

Objective. The yield and economic efficiency of hot-rolled strip production depends, to a decisive degree, on keeping within the required geometrical tolerances over the entire length of the rolled strip. The present article reports on studies of the production of hot strips that have homogeneous wi dth characteristics, particularly at the head- and tail-ends of the rolled material, minimal thickness deviations at the strip head-end, a homogeneous gauge profile without any wedge, and good flatness at the same time. It al so sets out to illustrate and assess specific measures and control concepts as means of improving the quality. Summary. The close combination of rolling-mill-campatible measuring techniq ues, the new installation of plant and equipment components, and their star t-up in rolling mills have been instrumental in hot strips being produced w ith homogeneous width characteristics, particularly at the head- and tail-e nds of the rolled material, as well as with minimal thickness deviations at the strip head-end, a homogeneous gauge profile without any wedge, and goo d flatness at the same time. The homogeneous width characteristics are achi evable by combining a suitable short stroke model with hydraulic edger roll gap setting systems in the roughing mill. The use of curved cropping shear blades at the entry to the finishing mill can considerably reduce the numb er of strip slippers during the initial pass phase of the bar in the finish ing mill, thereby avoiding any temperature-induced thickness deviations of the final strip due to prolonged bar residence times under the scalebreaker . To produce hot strips without any gauge profile wedge, it is necessary to preclude the lateral movement (tracking) of the in-process strip in the fi nishing mill. This is can be done by, among other means, implementing heavy , controllable guides at the entry to the finishing mill. The development o f a new measuring technique based on the projected fringe method, and the d evelopment of alternative process control methods and control algorithms, m ake it possible to optimise the strip flatness.