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The present research deals with the fish-scaling defect in enamelled thin-plate steel products. Hydrogen, absorbed into steel, particularly during the high temperature enamel-firing process, represents the main cause of this defect. At room temperature, the hydrogen released at the steel-enamel interface may build up in high pressures and break the enamel. From literature it is known that the steel fish-scaling resistance strongly depends on the hydrogen binding agents or trapping sites found into the metal.

The analysed steels were the usual comerciasl Al-killed and the and the newly appearing interstitial free (IF) steels. The production and optimisation of new enamelling IF steels, the clarification of hydrogen trap formation mechanisms in Al-killed and IF steels and the development of a new method to reveal the fish-scale susceptibility were the principal goals of the research. These were reached through a wide characterisation of steels, studying the effects of hydrogen on them and through the development of analytical techniques for the determination of fish-scale suuceptibility which could overcome the limits of usual methods.

Today, at the end of the research, a new, reliable and easy-to-use method which measures the trap site concentration and trap binding energy is finally available. If the number of traps is high enough, beyond a specified critical value and with a sufficient binding energy level, the steel will not fish-scale.

Additional information

Authors: FERA S, ILVA, Genova (IT);SOLINA A, University of Pisa, Pisa (IT);DE MICHELI D M, SM, Pisa (IT);DIGHERO A, SM, Pisa (IT);NAZIKKOL C, ThyssenKrupp Stahl, Duisburg (DE);WIENSTROEER S, ThyssenKrupp Stahl, Duisburg (DE);SCHNEIDER F, EKO, Eisenhuttenstadt (DE)
Bibliographic Reference: EUR 20950 EN (2004), 137 pp. Euro: 25
Availability: EUR-OP reference: KI-NA-20950-EN-S Available from EUR-OP sales agents URL:
ISBN: ISBN: 92-894-7736-9
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