Effect of applied stresses on signals from EMSPEC and 3MA systems based on magnetic behavior of steel

Meilland, Philip; ArcelorMittal Maizières Research; France

Meilland, P.; ArcelorMittal Global Research; France
Peyton, A.J.; University of Manchester; United Kingdom
Schmidt, R.; Arcelor-Mittal Eisenhüttenstadt; Germany
van den Berg, F.D.; Tata Steel; Netherlands
Yang, H.; Tata Steel; Netherlands

ID: ECNDT-0221-2018
Download: PDF
Session: Materials Characterization - ElectroMagnetic Techniques 2
Room: J2
Date: 2018-06-15
Time: 10:50 - 11:10

EMspec and 3MA magnetic based systems are promising for contactless on-line assessment of strip properties at e.g. the run-out table after hot rolling, the exit of continuous annealing and galvanizing lines. However, interpreting the system output signals in relation to the strip properties is not straightforward due to a number of complexities, of which the presence of low level stresses is of fundamental importance. In literature, studies on the sensitivity of the hysteresis B-H loops of Fe-Si electrical steels, to such low level stress parallel to magnetization, report a minor effect from tensile stresses, and a major effect from compressive stresses. Subsequently the stress level and moreover its orientation may have an impact on EMspec and 3MA measurements, which can be detrimental to the link with microstructure properties. However, little data is available on the subject, especially for the Advanced High Strength Steels.
For these grades the outputs of the EMspec and 3MA don’t give a direct reading of the B-H loops, thus requiring an experimental identification to report and understand the consequence of stress –whether applied or residual. For this, a specific tension test rig was assembled and industrial samples carefully prepared. As the application of compressive stress in the magnetization direction was not possible with thin strip samples, using several magnetizing field directions allowed indirect identification of the effect of compressive stresses via the Poisson effect. For the first time, the known effects of stresses on the hysteretic B-H loops could be transposed to the 3MA and EMspec signals. Such an analysis allowed in particular identifying the presence of residual compressive stresses in one of the samples.