Davy Mckee (Sheffield): Automatic Control of Steel Strip Thickness

Abstract

The problem of how to control a rolling mill so that the steel strip produced should be automatically held to close tolerances throughout its length of several thousand feet had been the subject of research work since before 1940. Two requirements were necessary, detection of variations in the gap and a response to remove or minimise these. Before the original innovation, measurement of strip thickness had to be made some distance away from the gap between the rolls. Further delay in response to deviations occurred while the operator adjusted the rolls, typically making several under- or over-corrections. Extensive investigations in the British Iron and Steel Research Association (BISRA) led to a patent being filed as early as July 1950, proposing that ‘load-responsive elements which will respond to variations in the separating force are incorporated in the mill and linked by mechanical, electrical and/or hydraulic means with the roll adjusting mechanisms in such a way that the desired relationship between the changes in separating force and roll setting is continuously maintained’. This concept was to lead both to the ‘Gaugemetcr’, featured in the Queen’s Award, and to the subsequent development of hydraulic control of the roll position gap.