Curling of Cold-Rolled Thin Strips

Abstract

It is considered that the curling of a cold-rolled thin strip is caused by an asymmetrical distribution of residual stress, but few studies have so far been made about it. This work has been carried out to study its origin by means of roll indentation tests and residual stress measurements. The results are summarized as follows:
(1) An identical relation was obtained between a rolling draught and a depth of roll indentation for every pass, and it was proved theoretically. Using this relation, the draught on the top or the bottom side of a strip could be known quantitatively from the indentation test.
(2) The longitudinal residual stress pattern over the thickness of every strip was approximated as a quadratic function.
(3) In case the diameter of the top roll was different from the bottom one, an asymmetrical residual stress distribution was introduced by the difference in draughts on the top and bottom sides.
(4) When rolled with inclined pass lines, asymmetrical residual stress patterns seemed to be caused by the difference in contact arc length between the top and bottom sides.
(5) The larger the front tention, the smaller became the curling curvature radius.