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Final report on Contract No 7210-TS/808, 204, 1 October 1996 to 31 March 2000.

The objective of this project was to investigate ways of enhancing the degree of control over product quality in the manufacture of heavy-gauge (1.0-3.0 mm) galvannealed strip. The focus of attention was the formability response (powdering, flaking tendency) arising from the alloy phase structure of the coating. The project was mainly laboratory-based and sought to develop an end-of-line powdering/flaking test, together with the establishment of release standards, and the construction of an online phase characterisation system.

A plant trial was carried out to produce material having varying degrees of alloying of the iron/zinc coating, ranging from pure zinc to >12% Fe, while maintaining mechanical properties essentially constant. The results from a number of simulative forming tests were compared with the flaking/powdering performance observed on a commercial pressing. The U-bead test gave the best all-round correlation with press performance for heavy-gauge galvanneal, especially with regard to powdering. Recommended release limits for acceptable performance have been established.

The online characterisation system incorporates an optical microscope with brightfield illumination, coupled to a CCD camera and frame-grabber. Signal processing is undertaken by a high-speed computer. The collected images gave reliable correlation with iron content of the coating (presence or absence of zeta crystals). Powdering could be predicted by means of digital image processing to within a 95% confidence level of the results given by the reflectometer.

Additional information

Authors: KAVANAGH C A, Corus UK Ltd, Port Talbot (GB);HARDY Y, CRM, Liège (BE)
Bibliographic Reference: EUR 20335 EN (2002), pp.168. Euro: 25.00
Availability: EUR-OP reference: KI-NA-20335-EN-S Available from EUR-OP sales agents. URL:
ISBN: ISBN: 92-894-3650-6
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