FOEN® air knives rank among the most advanced air knife systems in hot-dip galvanizing lines for coating all steel grades used in the automotive industry which places the highest demands on surface quality. The first integrated solution combining air knife and strip stabilization system was the FOEN DEMCO® system. Due to changes in design and constant improvement, it was advanced to the FOEN DEMCOJET® system. Thanks to the very compact design, the distance between air knife and the stabilization point of the electromagnet could be reduced to about 500 millimeters providing the basis to achieve an optimum coating result. Up to now, twelve FOEN DEMCOJET® systems for galvanizing lines have already been sold. The system was installed at reputed steel companies like Tata Steel (Netherlands), US Steel Kosice and Salzgitter and will soon be supplied to voestalpine, US Steel Protec, Ternium Pesqueria, Tata Steel UK, Stelco CA, Nucor, Hickman and CSN Galvasud. Further orders were awarded by HBIS Laoting for CGL 1 and 2.
Electromagnetic strip stabilization systems generally feature several electromagnets each nozzle arranged on both sides of the strip at the same height above the air knives. A position measuring sensor is installed below each magnet to continuously measure the distance of the magnet to the strip in a non-contact manner. The strip position determined by this sensor is compared to the target position. Through current variations in the coil it is possible to control the magnetic attraction acting on the steel strip and thus to equalize the strip profile and minimize strip movements.
Strip stabilization systems are a necessary feature in modern hot-dip galvanizing lines, since the requirements on process and surface quality are continuously growing due to various reasons. New industrial standards require closer tolerances, especially for the automotive industry. For example, the new European standard for the automotive industry (VDA 239-100) demands that the coil must not fall short of the minimum coating thickness value at no point. This makes the new standard stricter, since small deviations have a stronger impact on the evaluation. The trend towards higher- quality and more homogeneous surfaces requires a very stable strip run in the area of the air knives.