Sticking and scratching problems after batch annealing, including coil compression stress effects
The goal of the project was to study the specific conditions that appear between a strip and a roll when immersed in a fIuid, 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 in this study. It gives a formula for the thickness of film that tends to form between a foil wrapped around a roll, when this combination is immersed in a fIuid. Even if this theory is not developed for grooved surfaces, 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 decreases linearly with the speed until zero at hydroplaning speed. A roll speed measuring system was developed for use with 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. This sharply decreases for a crowned roll when dipped in water. Consequently, immersed rolls should no longer be viewed as having a higher risk of wrinkle generation, but as having a lower risk instead.
Bibliographic Reference: EUR 22059 EN (2006), 166 pp. Euro: 25
Availability: Katalogue Number: KI-NA-22059-EN-S The paper version can be ordered online and the PDF version downloaded at: http://bookshop.europa.eu
ISBN: ISBN: 92-79-01747-0
Record Number: 200618698 / Last updated on: 2006-09-14
Original language: en
Available languages: en