Dobmann G., Development and qualification…


Development and qualification of the Eddy-Current testing techniques “EC” and “EC+” in combination with Leeb-Hardness-Measurements for detection and verification of hardness spots on heavy steel plates


Gerd Dobmann, Christoph König, Uwe Hofmann, Gerald Schneibel

Hardness Spots are local areas with increased hardness on the surface of semi-finished or end products in steel manufacturing. The cause of these hardness spots is attributed to effects in the casting or rolling process. As of stochastic nature, only a reliable non-destructive testing (NDT) technique, applied as a 100% surface examination can detect infected areas, of which, the individual hardness value is verified, by performing Leeb hardness measurements, in accordance with the given standard. The NDT-techniques developed by DILLINGER and Rohmann, to detect the hardness spots, are due to an Eddy Current (EC) procedure which in two consecutively developed variants came into application, named EC and EC+. Whereas the EC procedure is asking for shot-blasted surfaces, to remove the rolling skin (scale), avoiding larger scatter in the EC-impedance data, the EC+ procedure is applied without shot blasting. The contribution reports to the systems and the development of an Inspection and Testing Program (IPT) which was qualified, according the guidelines of the British Standards Institution PD CEN//TR 14748. Special emphasis is on the discussion of reliability.
NDT, Eddy Current application, hardness spots

Proceedings of 46th National Conference on Nondestructive Testing (KKBN),
17-19 october 2017, Starachowice, Poland

Online publication date

14 december 2017


Nondestructive Testing and Diagnostics, vol. 2, no. 3, pp. 24-31, 2017