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

Speaker:
Böttger, D.; Fraunhofer Institute for Nondestructive Testing IZFP; Germany

Authors:
Böttger, D.; Fraunhofer Institute for Nondestructive Testing IZFP; Germany
Gabi, Y.; Fraunhofer Institute for Nondestructive Testing IZFP; Germany
Straß, B.; Fraunhofer Institute for Nondestructive Testing IZFP; Germany
Wolter, B.; Fraunhofer Institute for Nondestructive Testing IZFP; Germany
Conrad, C.; Fraunhofer Institute for Nondestructive Testing IZFP; Germany

ID: ECNDT-0453-2018
Download: PDF
Session: Materials Characterization UT
Room: G1
Date: 2018-06-13
Time: 15:20 - 15:40

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 scaped material is conform in order to be processed. This generates a huge amount of pseudo scrap. The total costs of material loss 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 measurement information from micro-magnetic 3MA technique and ultrasound time-of-flight measurements. The developed NDT device and sensors are firstly used for laboratory investigations as well as for in-plant measurements after some adaptations.
For this purpose, several mock ups from different material grades and thickness from production plate are prepared and calibrated in situ conditions. Correlation between mechanical properties (Rm, Rp0.2,..) and the combined micro-magnetic (Hcu, Hcm,..) and ultrasound output parameters (time-of flight) are established. Furthermore, statistical studies are realized in order to optimize and adapt the calibration to inline measurement by adding most influent environmental parameter. The concept is proven by combining micro-magnetic, ultrasound parameters and temperature, so that mechanical properties could be assessed with good accuracy.