Characterization Methods along the Process Chain of Electrical Steel Sheet-From Best Practices to Advanced Characterization.

Sandra Korte-Kerzel,Martin Heller,Kay Hameyer,Rudolf Kawalla,Wolfram Volk,Xuefei Wei,Anett Stöcker,Nora Leuning,Lucas Böhm,Gerhard Hirt

doi:10.3390/ma15010032

Abstract

Non-oriented (NO) electrical steel sheets find their application in rotating electrical machines, ranging from generators for wind turbines to motors for the transportation sector and small motors for kitchen appliances. With the current trend of moving away from fossil fuel-based energy conversion towards an electricity-based one, these machines become more and more important and, as a consequence, the leverage effect in saving energy by improving efficiency is huge. It is already well established that different applications of an electrical machine have individual requirements for the properties of the NO electrical steel sheets, which in turn result from the microstructures and textures thereof. However, designing and producing tailor-made NO electrical steel sheet is still challenging, because the complex interdependence between processing steps, the different phenomena taking place and the resulting material properties are still not sufficiently understood. This work shows how established, as well as advanced and newly developed characterization methods, can be used to unfold these intricate connections. In this context, the respective characterization methods are explained and applied to NO electrical steel as well as to the typical processing steps. In addition, several experimental results are reviewed to show the strengths of the different methods, as well as their (dis)advantages, typical applications and obtainable data.

Highlights

Characterization as the Basis for Tailor-Made MaterialsIn the course of its more than 100-year history, NO electrical steel sheet has become a high performance and essential material in today’s society
The domain structure is mostly considered in academia (Bitter imaging [64], neutron grating interferometry [66]), if reference Bitter imaging patterns of specific characteristics, such as high residual stresses, unfavourable orientations or grain boundaries, can be identified, it could become a great tool to quickly access qualitative data about the final magnetic properties based on the microstructure and texture
Innovation is often enabled by characterization methods

Summary

Introduction

In the course of its more than 100-year history, NO electrical steel sheet has become a high performance and essential material in today’s society This is because the efficiency of rotating electrical machines, in which thin, stacked electrical steel sheets are mainly used to guide and magnify the magnetic flow, is key to reducing the overall environmental impact, which, on the other hand, is important in view of climate change and a rising demand for “clean” electrical machines (transportation—electric vehicles, energy sector—generators of wind turbines, household machines—mixers, etc.). Tailor-made materials and microstructures are especially important because rotation frequencies of the respective electrical machines have a large impact on the magnitude and share of the different iron loss components (hysteresis, classical and excess losses), which, in turn, depend on different material and microstructure properties like alloying elements, grain size, texture, sheet thickness or residual stresses.

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