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The aim of the project was to determine how hot rolling and pickling parameters influence the surface quality of cold rolled and galvanised products and what measures can be taken to increase this surface quality.

The research consisted of:
- determining the influence of inhibitors on hydrogen permeation and surface appearance of pickled material;
- industrial pickling and cold rolling pilot plant trial on re-phosphorised IF steel, by varying three parameters: i.e. cooling after hot rolled coiling, pickle time and edge/middle part;
- induction pulse pickling on the pilot line to enhance the pickling process;
- galvanising experiments on Rhesca pilot simulators of steel samples pickled under different pickling conditions.

Steel strip samples for and after the trials (hot rolled, pickled, cold rolled, annealed or galvanised) were examined for their surface characteristics like topography, morphology, roughness parameters, elemental surface enrichments, surface appearance, surface cleanliness.

In a parametric study towards the pickling and cold rolling of a rephosphorised Ti-SULC grade it was found that the middle parts in the coil show a lower surface cleanliness than the edge parts. This could be explained by grain boundary oxidation enhanced by phosphor enrichment in grain boundaries. This phenomenon was also confirmed in laboratory experiments. The pickling time and the cooling rate of hot rolled coils (below 480 °C) had little or no influence. It was concluded that local enhancement (edge) of the pickling process will lead to more consistent pickling processes. Techniques like turbulent spray pickling or induction pulse pickling can be used for this purpose.

Additional information

Authors: VAN 'T HULL J P, CORUS NL, IJmuiden (NL);SUSSEK G, Thyssen Krupp Stahl AG, Duisburg (DE);CRAHAY J, CRM - Centre de recherches métallurgiques, Liège (BE)
Bibliographic Reference: EUR 20893 EN (2003), 164pp. Euro:25
Availability: EUR-OP reference: KI-NA-20893-EN-S Available from EUR-OP sales agents URL:
ISBN: ISBN: 92-894-6311-2
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