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The goal of the project was to study the specific conditions that appear between a strip and a roll when immersed in a fluid, which can be ‘zinc’ on galvanising lines or ‘close to water’ on tinning lines. The foil bearing theory developed in the bibliography was a guideline for this study. It gives a formula for the film thickness that tends to form between a foil wrapped around a roll, when this system is immersed in a fluid. Even if this theory is not developed for a grooved surface, it gives reasonable results when considering the equivalent roughness of the grooving. Trials in water pilots show or confirm that roughness and grooving pattern have a tremendous effect on hydroplaning speed. Adherence measured by the transmissible torque de creases linearly with the speed until zero at hydroplaning speed. A roll speed measuring system was developed for use in zinc. On a galvanising pilot line of CRM, no strip/roll slippage was detected in any conditions with a grooved roll, but stop-and-go behaviour was detected for a roll without grooves. One month of data logging on a galvanising line of Eurogal, Flémalle, Belgium, brought only one case of slippage: thin strip (0.187 mm) and high speed (140 m/min), with a grooved roll. Good agreement was found between all the trials in water and in zinc with the foil bearing theory. The risk of fold formation was also studied. It sharply decreases for a crowned roll when dipped in water. Consequently, immersed rolls should no longer be looked at as higher risk of wrinkle generation, but as a lower risk instead.

Additional information

Authors: BERTRANDIE J J, Arcelor Research (IRSID), Maizières-lès-Metz (FR);GAGNON A, CRM - Centre de recherches métallurgiques, Angleur (BE)
Bibliographic Reference: EUR 21788 EN (2005), 69 pp. Euro: 15
Availability: (Catalogue Number: KI-NA-21788-EN-S)
ISBN: ISBN 92-79-00060-8
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