NDT of austenitic steels – Evaluation of spot weld nugget diameters by imaging analyses of the residual magnetic flux density

Mathiszik, Christian; Technische Universität Dresden; Germany

Mathiszik, C.; Technische Universität Dresden; Germany
Reinhardt, T.; Technische Universität Dresden; Germany
Zschetzsche, J.; Technische Universität Dresden; Germany
Füssel, U.; Technische Universität Dresden; Germany

ID: ECNDT-0478-2018
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Session: Transportation, railway & automotive 2
Room: R2
Date: 2018-06-13
Time: 16:00 - 16:20

Non-destructive testing (NDT) of resistance spot welding compounds continues to pose a great challenge. The nugget diameter is the most important quality criterion. Established ultrasonic-based methods reach their limits when evaluating the nugget diameter of combinations with significantly different sheet thicknesses and with deep electrode indentations. In these cases, the imaging analysis of residual flux density shows high potential. Previous results of this NDT method concentrate on spot weld combinations of ferromagnetic steels. Hence, latest research at Technische Universität Dresden focuses on the application of the imaging analysis of residual magnetic flux density on spot welds using austenitic steels. Due to the high cooling rates after welding delta ferrite with ferromagnetic properties is generated inside the nugget, and therefore the residual magnetic flux density can be measured.

The talk will show the measuring concept of the NDT method for spot welds and presents the results of its application on two and three sheet metal combinations of austenitic steels.