Method of producing grain orientation in electrical steel lamellae to reduce iron losses

• Applicants: Professor Dr.-Ing. Bernd-Arno Behrens; Dr.-Ing. Bernd Wolter
• Subject Area: Primary Shaping and Reshaping Technology, Additive Manufacturing
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 561134853

The goal of this research project is to achieve a reduction in iron losses in electrical sheets of stators in rotating electrical machines in order to increase efficiency. The focus is on reducing iron losses, which can be influenced by grain orientation. Nowadays, the magnetic core of electrical machines consists mainly of iron-silicon electrical sheets stacked in thin laminations. The laminations are a crucial component, especially for stators in electric motors. Due to the ferromagnetic properties of the electrical sheet laminations, they conduct magnetic flux. The magnetic properties of the electrical steel laminations are therefore decisive for the efficiency and energy efficiency of an electric motor. Of particular importance here are the remagnetization losses, which describe the dissipation of energy. These losses are particularly large for the high-revving motors of electric vehicles and significantly impair the efficiency and thus the motor performance and range of the vehicles. Due to growing demands for climate protection as well as the automotive industry's aspirations for increasingly efficient electric motors, the development of low-loss electric laminations is a research area with high economic and ecological potential. In order to develop efficient methods for the production of radially grain-oriented electrical steel laminations, a radial rolling process for adjusting this grain orientation is being developed. For this purpose, sheet metal plates are to be rolled over in radial direction step by step with changing angles of attack. The rolling pass, the angular offset and the rollover frequency will be varied. The focus is on identifying the optimum process parameters for achieving the highest possible graded magnetizability. The change in shape achieved (degree of deformation) can be calculated analytically with the aid of volume constancy. The sheet distortion that could occur during the forming is eliminated by a downstream drawing process. Preliminary investigations of the influence of forming on the magnetic properties of cylindrical samples were carried out in ring compression tests at the IFUM. Here, an improvement of magnetizability in the range of 55 % in the grain direction could be achieved. A transfer of the results to a radial grain orientation is planned for the envisaged research project. Measurement technologies based on the 3MA testing technique will be developed at the IZFP, which will allow the local determination of anisotropic electromagnetic properties of the electrical sheets after different processing steps. A simulation of the changing magnetic properties will take place iteratively with the performed experiments. In addition, the residual stresses in the workpieces are measured at the IFUM. From this, a model is being developed with which the influence of the process parameters on the isotropy of the magnetizability of the semi-finished products can be determined.

• DFG Programme: Research Grants