When steel or aluminum strip is processed in hot rolling mills, the width of the material can only be specifically controlled in the roughing mill. In downstream processes, this targeted influencing of the width is either not possible at all or possible only to a limited extent, which is why the material usually has to be produced with a certain excess width, which then needs to be trimmed and scrapped later on during cold processing. By reintroducing the trimmed scrap into the production cycle, the width accuracy that can be achieved in the hot rolling mill has a significant, direct influence on the resource efficiency, CO2 balance, and costs of the manufacturing process.
Attaining the desired strip width with a high degree of accuracy requires not only the ability to influence the width using suitable actuators and an appropriate control system, but also a sufficiently precise, reliable and cost-effective measuring system, which is able to function permanently under the harsh ambient conditions (water, vapor, and extreme heat) of a steel roughing mill. Following unsuccessful trials in this area involving various different technologies, single-channel radar systems for measuring the width have recently been employed in steel roughing mills. However, the limitation of such systems, which are restricted to just one measuring channel, is that ski ends on head and tail of the strip as well as the uneven contour of the strip have a negative impact on the accuracy of the measurements, therefore the use of the width signal for feedback width control is not a straightforward option.