Hot strip flatness optimization by means of edge masking in the ROT

Abstract

The control of temperature distribution across the strip is essential for the hot strip flatness improvement. Hot strips of Arcelor in Avilès may display wavy edge defects that are generated after the finisher and are attributed to residual stresses introduced by the accelerated cooling on the runout-table. A first approach has established that the thermal drop on the run-out-table has a significant effect on flatness, at the edges in particular. Among several systems that may control temperature at the edges, the edge masking technology has been selected, considering the previous implementation on CSP mills. Wavy edges are considerably removed or even suppressed on the operator side, while they are reduced but not eliminated on the drive side.

Calculation of thermal stress affecting strip flatness change during run-out table cooling in hot steel strip rolling

“…If the edge wave is not prevented, the flatness control in the finishing mill becomes worthless (Yoshida, 1984c). Conventional means to solve this problem are improving temperature distribution uniformity along transverse direction (Naoki and Hiroshi, 1995;Peregrina et al, 2006) through controlling water flow rate distribution and edge masking amount. However, both the measures mentioned above need modify and install new devices and their control system.…”

On-Line Flatness Measurement in the Steelmaking Industry

“…The evolution of the temperature distribution of the rolled product during cooling is also of utmost importance to avoid flatness defects [9]. If the rolled product is cooled very fast, residual stresses may cause non-flat edges [17]. Furthermore, the flatness of the rolled products may be affected in other manufacturing stages, such as coiling, cutting and lifting, among others.…”

“…Among them, the most important are: ( i ) on-line and off-line visualization techniques to adequately provide flatness measurements to human operators in rolling mills [65]; ( ii ) compensation for uneven temperature across the width of the rolled product while rolling to avoid flatness defects caused by different temperature profiles [9]; and ( iii ) modeling for flatness optimization in hot-rolling mill processes [17]. …”

A Numerical Study on the 2-D Temperature Distribution of the Strip on Run Out Table of the Hot Mill

“…The suitability of different numerical methods for the solution of the proposed model equation from the point of view accuracy and computation times is studied. Peregrina et al [5] established that the thermal drop on ROT has a significant effect on flatness, at the edges in particular. The edge masking technology has been selected to control the temperature at the edge of the strip.…”