Innovative non-contact, non destructive sensors for automatic detection on surface and internal defects in hot continuously cast products


This was a RFCS project involving VDEh-Betriebsforschungsinstitut GmbH (BFI), Tata RD&T Teesside Technology Centre (formerly Corus), Arcelor Mittal R&D Technology Center – Centro Desarollo Tecnológico and Scuola Superiore Sant’Anna (SSSA).
The focus was to develop innovative non-contact, non-destructive sensors for automatic detection of surface and internal defects in hot continuously cast products.

A technique, based on the ultrasound pulse-echo-method, has been developed through technique using noncontact EMATs to both generate and receive ultrasonic signals.  The use of the developed Phased-Array system has been investigated for surface and sub-surface defects. The inspection system can find defects on steel products, even if the surface is rough, contains oscillation marks and scale oxide. A prototype Laser-EMAT system has been developed.  This has been installed on the
Pilot Caster at Tata Steel. Extensive trials have been carried out on cold steel samples below the Curie temperature with good results but hot steel trials have been of limited success. The Laser-EMAT device has been equipped  with complete software for data visualisation and analysis and the necessary tools for ultrasound data interpretation has been also developed.

As a result, defects such as very thin and zigzag cracks can now be reliably detected. A system to check the quality during and after scarfing was developed and integrated in the plant. A software tool for tracing slabs through the mill was developed allowing the evaluation of the defects.

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