Hot dip galvanizing - Stabilising and cooling the strip in the wiping area
A uniform hot dip galvanised coating requires a stable position of the strip during gas wiping. The objective of the present work is to improve coating homogeneity of hot dip galvanised product by three actions: - optimised air pad stabiliser (CRM); - improved bearings of the bath rolls (BFI); - detection and analysis of online wiping instabilities (Aceralia). Air pad prototypes were characterised (pressure profiles and total force) on a laboratory scale in order to optimise the ratio return force on pressure gradient (impact on liquid Zn). A significant stabilising effect of the air pad was measured by inductive sensors on an industrial scale (factor 2 on the RMS in the wipers). No associated waviness was revealed by surface profile measurement. A wear testing apparatus was designed and built. After preliminary tests, the tribological behaviour of different materials was investigated. The material combination Stellite 4 sleeve against SiN bars was finally shown to be the best. Guiding rules suggest having a radius r both on the bearing area of the new ceramic bearing and on shaft of the pot roll. The depth of the radius should be 2-4 mm. A system using thermal information provided by an infrared camera was developed on the galvanising line No 2 (Aceralia, Aviles). The system is aimed to detect online coating profile problems derived from bad knives' conditions. An alert could be sent to the monitoring system when relevant deviation with information from the process computer is detected.
Bibliographic Reference: EUR 22035 EN (2006), 84 pp. Euro: 15
Availability: Katalogue Number: KI-NA-22035-EN-S The paper version can be ordered online and the PDF version downloaded at: http://bookshop.europa.eu
ISBN: ISBN: 92-79-01409-9
Record Number: 200719292 / Last updated on: 2007-07-10
Original language: en
Available languages: en