Galvanising by the zinc cushion process
An easy way to coat strips with zinc alloys is the 'hot-dip' process (continuous dip of strips in liquid metal). At CRM, a new coating process, characterised by floating strips and by no moving immersed equipment touching strips, has been developed. This method (liquid zinc cushion) has been tested in a pilot line, confirming that it could be used with success as coating process. Amongst other advantages, zinc circulation allows continuous control of its temperature, with heat exchangers. It also gives the ability to galvanise dual-phase steels by quenching in liquid zinc. It was of major importance to gather all technical information for building industrial trials and to evaluate economic aspects. For analysing the potential of the technique, efforts have been made in fields of modelling, simulating and product processing. Developments in exchangers, pumps and filtering have helped to solve the difficulties encountered. The technical efficiency of this technology has been validated and a cost estimation has been made. Considering cushion aspects, it has been noted that system maintenance is difficult to manage (conventional sink roll was also improved). For higher line speeds (> 200 m/min), it can bring a solution to potential roll slipping and stoppage situations. For quenching aspects, it was shown that enhancing dual-phase properties of several steel grades of lower cost was feasible by cooling strips directly in liquid zinc. Although implementation in new line is easier, it remains possible to transform existing lines. Development of galvanisable HS steels led actually to some production of DP600 steel of higher cost. A balance must be achieved between both choices.
Bibliographic Reference: EUR 22968 EN (2007), 196 pp. Euro: 25
Availability: Katalogue Number: KI-NA-22968-EN-S The paper version can be ordered online and the PDF version downloaded at: http://bookshop.europa.eu
ISBN: ISBN: 978-92-79-06509-5
Record Number: 200819645 / Last updated on: 2008-01-21
Original language: en
Available languages: en