Research in Engineering and Aviation

Filtering Winding Effects from Control Systems in Cold Rolling Operations

May 2011

Author(s): Hinton, J., , Malik, A.S., Grandhi, R.

AIST Annual Conference, May 2-5, 2011, Indianapolis, IN

Abstract

The increased demand for high quality thin gauge metals has prompted the improvement of quality control systems during the cold rolling process. The presented work discusses stress growth in a strip during the rolling/winding process that has a “wedge” thickness profile: a semi-parabolic, asymmetric cross-section.  During rolling, current control systems with flatness meters (sensors) are unable to differentiate between “rolled-in” stresses caused by the work rolls, from stresses caused by the winding process. The accumulating effects of winding a strip with a wedge profile increases the potential of the flatness meters to measure a false stress profile which may lead to incorrect mill adjustments. To aid in accurate control system adjustments, a preliminary method is developed to separate the winding stress contribution from the overall stresses that are measured indirectly by a flatness control system. The in-plane stresses and corresponding flatness resulting from winding a strip containing wedge are computed using a conventional one dimensional elasticity method, as well as a two dimensional Airy function method, based on strip geometry, boundary conditions, and planar spatial position on the strip. The Airy method is shown to give position dependent and non-intuitive stress distributions whereas the conventional technique gives more intuitive results while not being position dependent down the length of the strip.   Prediction of the stress field throughout the winding process allows for the filtering of elastic/plastic winding effects from the flatness control system. This permits more appropriate control corrections for the plastic flatness defects that result from the distribution of thickness reduction.