Abstract
M.Ing.
Columbus Stainless, a subsidiary of Acerinox, manufactures stainless steel in
their plant located in Middelburg, South Africa. During the hot rolling
operation the steel is rolled on a 4-high finishing mill where strip movement
perpendicular to the rolling direction occurs. This movement is undesirable
because it causes inferior product quality and may also lead to downtime if
the strip moves past the edge of the rolls. In the past the operator made
adjustments to the relative alignment of the rolls in the mill in an attempt to
limit the sideways movement of the strip. In order to improve product quality
and production throughput, the manual action of adjusting the parallelism of
the rolls was replaced with an automatic steering control system. Analysis of
the process revealed that several variables have an impact on the way the strip
reacts to changes in the alignment of rolls in the mill. An adaptive fuzzy logic
control system was designed and implemented in the real time control system
of the mill. During commissioning the system did not have an adverse effect
on production and all initial project criteria were met, as was stipulated in
Section 1.4 of this document. The control system improved the strip
movement by an average of 11% on various products rolled. Based on
production data, the system potentially prevented two coils from leaving the
rolls during the month long evaluation period and saved 40 minutes of
production time. If the savings in material losses and the potential gain in
production time are added the possible anticipated monetary saving is
estimated to be about 24 million Rand a year.