The application of electromagnetic measurements for the assessment of skin passed steel samples

Peyton, Anthony, Karimian, Noushin, Wilson, John, Stolzenberg, M, Schmidt, R, Davis, Claire, Lombard, P, Meilland, P, Martinez-de-Guerenu, A and Gurruchaga, K (2016) The application of electromagnetic measurements for the assessment of skin passed steel samples. In: 19th World Conference on Non-Destructive Testing (WCNDT 2016), 13 June 2016 - 17 June 2016, Munich, Germany.

Preview

Published Version Available under License Creative Commons Attribution. Download (1MB) | Preview

Abstract

This paper begins by exploring the relationship between magnetic properties such as coercive field, RMS Magnetic Barkhausen Noise (MBN), initial and differential permeability and percentage elongation of skin passed samples for three different steels; interstitial free, micro alloyed and dual phase. A closed magnetic loop system is used to measure the fundamental magnetisation properties and a system based on an impedance analyser and a cylindrical coil is used to determine low field differential permeability. The results show that coercive field increases consistently with increasing percentage elongation for all three steels, as increasing material hardness causes an increase in magnetic hardness and a corresponding increase in coercive field. This effect levels off at higher values as dislocation density saturates. As would be expected, the inverse trend is observed for differential permeability. Similar results are also reported for MBN and initial and low field differential permeability measurements for the interstitial free and dual phase steel, but the behaviour for the micro alloyed samples appears to be more complex. Finally, the paper considers the response of two on-line measurement systems that exploit these magnetic relations. The first system applies pulse excitation and measures the resulting remnant magnetisation and the second analyses the harmonic response from AC excitation. Both systems can detect microstructural changes associated with varying magnetic properties during strip production.