EXPERIMENTAL-MEASUREMENT OF CURL IN ROLLING

In this paper, the problem of curl in flat rolling is reviewed. A. sim ple method of quantifying curl is described and experimental results a re presented. A simulation of curl is also performed using off-the-she lf metal forming software. Using the experimental results, a value cal led the curl number is obtained. Experiments were run to verify the si mplicity of the curl number ratio. The experiments showed that curl re verses when reduction is the only variable. Using the curl number, the operating region for a specific mill producing a flat sheet can be de termined. Speed is also shown to have an effect, but is not as importa nt as reduction, as has been assumed in previous studies. A two-high m ill with 102 mm diameter work rolls and a variable speed drive was use d for the experiments. The shapes of the rolled billet samples are dig itized into discrete x and y points in a text file using a common digi tizing tablet. These are then used to obtain a curl number. The proces s was also modelled with DEFORM, which shows that curl occurs for diff erent roll speeds and different values of surface friction, but does n ot show the reversal of curl with reduction as was found in these expe riments. (C) 1998 Elsevier Science S.A. All rights reserved.