On-Line Eddy Current Inspection of Steel Ingots

The FraunhoferInstitute for Nondestructive Testing (IZFP), the Institute of Welding and Materials Testing and Ro-QNet exercised a new eddy current inspection technique to detect and characterize surface cracking of as-rolled, square-shaped billets and to identify deviant steel grades to exclude possibel material mix-up. The objective was to demonstrate the technique's potential with respect to optimization of flaw detection and characterization. The measurements at the specimen containing artificial and natural surface cracks, having different steel grades (variations in chemical composition exhibit that the multi-frequency eddy current method is capable to detect and characterize surface breaking flaws with any given orientation having depths of approximately 0.6 mm on the flat exterior surface of the billets and depths of 2 mm of larger in the edge region if the flow length equals of exceeds 20 mm. Distrubances or interference caused by fixed scale layers and/or different material mi crostructure reduce the accuracy of flaw depth evaluation.