Eigenschaftsbeeinflussung von nicht kornorientiertem Elektroband mittels Lanthan

Dahlmann, Christoph; Bleck, Wolfgang (Thesis advisor); Hameyer, Kay (Thesis advisor); Krupp, Ulrich (Thesis advisor)

Aachen : RWTH Aachen University (2022, 2023)
Dissertation / PhD Thesis

Dissertation, Rheinisch-Westfälische Technische Hochschule Aachen, 2022

Abstract

Soft magnetic electrical steel plays a decisive role in the transformation of electric into kinetic energy. However, the electric energy cannot be converted into kinetic energy without losses, so a part of the energy input is converted into heat. The heat losses should be kept as low as possible in order to increase efficiency and reduceemissions. This can be achieved through the help of targeted alloy development. Due to the large amount of non-grain-oriented electrical steel in all kinds of electric motors and generators, there is an enormous potential to significantly contribute to the energy transition and electromobility. Thus, the investigations of the NOelectrical steel dealt with in this thesis occupy an essential place. To investigate the influence of impurities in the structure of the rolled material on the magnetic properties of non-grain-oriented electrical steel, four electricalsteel alloys with different lanthanum contents were produced. Lanthanum was chosen because it is able to reliably bind off the elements that cause impurities, sulphur and oxygen, and thus positively influence the properties of the material. An industrially used alloy concept with 2.9 wt.−% Si served as a basis for this work. The material was cold rolled to a final thickness of 0.5mm and subjected to different final annealing cycles to determine the influence of grain growth on the resulting magnetic properties. Furthermore, the influences on the texture, polarisation, andstrength properties were investigated to enable a holistic characterisation of the material. By varying the lanthanum content between 102 to 154 ppm and the final annealing parameters, it could be shown that lanthanum has a positive influence on the remagnetisation losses, especially in the low frequency range due to the significantlyaccelerated grain growth. Increasing the measuring frequency leads to a strong increase in losses due to the grain size, but the comparison of similar grain sizes of the alloys without and with lanthanum showed an apparent advantage due to reduced excess losses. Investigations of texture and saturation polarisation showed no clear influence of lanthanum. However, the significantly increased grain size with the same heat treatment led to slightly reduced tensile strength properties. A direct influence of the lanthanum on the matrix strength of the material was, however, excluded. As a result of the investigations, it can be stated that lanthanum is in principle capable of positively influencing the magnetic properties of non-grain-oriented electrical steel.

Institutions

• Division of Materials Science and Engineering [520000]
• Chair of Materials Engineering of Metals and Department of Ferrous Metallurgy [522110]