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Combination of both ultrasound and 3MA NDT technique for mechanical parameters calibration on heavy plates

: Böttger, David; Gabi, Yasmine; Straß, Benjamin; Wolter, Bernd; Conrad, Christian

Merck, Peter (Ed.) ; European Federation for Non-Destructive Testing -EFNDT-:
12th European Conference on Non-Destructive Testing, ECNDT 2018. Proceedings : Gothenburg, Sweden, 11-15 June 2018; CD-ROM
Gothenburg: Sweden MEETX AB, 2018
ISBN: 978-91-639-6217-2
Paper ID-ECNDT-0453-2018, 4 pp.
European Conference on Non-Destructive Testing (ECNDT) <12, 2018, Gothenburg>
Conference Paper
Fraunhofer IZFP ()
magnetic testing; ultrasonic testing; NDT

Cold resistant steel qualities for heavy plate construction like pipes require a hot rolling thermo-mechanical control strategy at the last passes in the intercritical domain. As a result, the plates are textured, with altered material properties at the extremities due to natural cooling gradients. Such areas called 'cold ends' will end in unacceptable local properties (especially Rm and Rp0.2), which presently require cropping as scrap. Usually the cold ends are cut off with large safety margins, because the precise location of the transition zone between OK and NOK material quality is not known. Based on destructive tests, it has to be assured that the material fulfills all conformity requirements in order to be further processed. This generates a huge amount of pseudo scrap. The total costs of material losses from pseudo scrap for European steel industry is over 2.5 million EUR /year. Fraunhofer IZFP suggested an alternative solution which allows quick determination of the precise location of the separator line between OK and NOK material. The non-destructive testing (NDT) solution of IZFP is based on the design, construction and assembly of a scanning device combining two different non-destructive testing techniques namely micromagnetic material characterization technique (3MA) and ultrasound time-of-flight measurements based on an electromagnet acoustic transducer (EMAT). The developed NDT device and sensors are used for laboratory and in-plant investigations. For this purpose, several mock ups from different material grades and thickness from production plates are prepared and calibrated in situ conditions. Correlation between mechanical properties (Rm) and the combined micro-magnetic (e.g. Hcu, µmax, K, etc.) and ultrasound output parameters (time-of flight differences) are established. Furthermore, statistical studies are realized in order to optimize and adapt the calibration to inline measurement by adding the most influencing environmental parameters. The concept is proven by combining micro-magnetic, ultrasound and temperature parameters, so that mechanical properties could be assessed with good accuracy.