New Mini-SST for Advanced Characterization of Electrical Steel

03/07/2020

On July 3rd, 2019, a new type of miniature single-sheet tester (Mini-SST) was put into operation at the IEM's Laboratory for magnetic materials. The SST was procured within the DFG Research Group "FOR 1897 - Low-Loss Electrical Sheets for Energy-Efficient Drives" (255713208) and was designed in cooperation with Brockhaus Measurement Systems.

  Picture of a miniature SST Copyright: IEM Miniature SST

The miniature SST is used to study the magnetic properties of single, bi or oligocrystals. With this method, the influence of grain boundaries, crystal orientation or dislocation density on the magnetic properties of iron silicon (FeSi) electrical steel can be quantified in order to transfer the results to polycrystal behavior and use them for modeling. Within the DFG project, investigations on the influence of mechanical stress and strain are performed in cooperation with the Institute for Physical Metallurgy and Materials Physics (IMM) at RWTH Aachen University in order to magnetically characterize single and bicrystals in the undeformed and deformed state. This new approach is expected to provide additional insights into the interaction of grain boundaries with the cutting process and into the effects of the combination of very thin sheets and coarse grains - in the order of magnitude of the sheet thickness.

  Image of the magnetic domain structure Copyright: IEM Bicrystalpreparation and Bitter-Image of the magnetic domain structure

Since the sample sizes resulting from single crystal growth are in the order of 2 cm², a correspondingly small SST had to be developed. The outer distance between the magnet yoke legs is 22.3 mm. The resulting sample size is 25 mm x 10 mm. The primary and secondary winding system has 60 turns each. The SST is controlled by the MPG software. Within this framework, a numerical air flow compensation is used.

  Partners and Funding Copyright: IEM