Application-oriented materials engineering of non-grain oriented electric steel sheet

  Micrograph of fully finished electic steel sheet Copyright: IEHK Micrograph of fully finished electic steel sheet

Increasing requirements regarding energy generation and energy transformation lead to steady optimization of rotating electrical machines. Those machines, especially electric motors, use non-grain oriented electric steel sheets as material for stator and rotor. To increase the efficiency of the electric machines, the materials are consequently improved and optimised for the intended purpose.

The improvement of the ferritic, soft magnetic steels is based on the reduction of the iron losses, which occur during application. The sum of the losses can be reduced by reducing the thickness of the steel sheets, increasing of the specific electrical resistance or a coarser grainsize. Rising the specific electrical resistance is done in general by alloying silicon or aluminium, which in return reduce the cold formability. The coarse grainsize is adjusted during the final annealing. Annealing temperature, annealing time and alloy design have a big influence on the grain growth.

The research focus of the steel institute (IEHK) is the investigation of the complete process chain of the electric steel sheet production. Also a customized alloy design is part of the research. The Influence of heat treatments, forming processes and alloying and their interaction is evaluated. Finally, the impact of the process parameters on iron losses and crystallographic texture is analysed.