Anett Stöcker

Evolution and Interaction of the Microstructure and Texture at the Different Processing Steps for Ferritic Nonoriented Electrical Steels

The fabrication process of nonoriented electrical steels comprises casting, hot rolling, cold rolling, and final annealing. The development of new technologies for the fabrication of hot band offers new possibilities. In this paper, we will shortly describe the similarities and differences with respect to the evolution of microstructure (grain structure) and texture along the conventional processing route and thin strip casting. We will point out the most relevant features at the different processing steps, which are important for the optimum texture and microstructure of the finally processed material. Thereby, we will regard ferritic FeSi steels, where no homogenization of the microstructure appears due to the austenite-ferrite phase transformation.

Influence of cubic texture intensity of hot rolled ferritic non-oriented electrical steels on the microstructure and texture in the final processed material

The magnetic properties of non-oriented electrical steels are determined by the microstructure and texture of the material. Besides optimum grain size (microstructure) for low values of specific magnetic losses, a high intensity of θ-fibre texture and low intensity of γ-fibre and α-fibre texture is desirable. Each of the processing steps influences the intensity of the θ-fibre in the final processed material. In this paper the interplay of the various processing steps on the intensity of the θ-fibre is regarded for ferritic Iron-Silicon steels with 2.4 wt.% Si and 3.0 wt.% Si.

Impact of the interaction of material production and mechanical processing on the magnetic properties of non-oriented electrical steel

Thin laminations of non-grain oriented (NO) electrical steels form the magnetic core of rotating electrical machines. The magnetic properties of these laminations are therefore key elements for the efficiency of electric drives and need to be fully utilized. Ideally, high magnetization and low losses are realized over the entire polarization and frequency spectrum at reasonable production and processing costs. However, such an ideal material does not exist and thus, achievable magnetic properties need to be deduced from the respective application requirements. Parameters of the electrical steel such as lamination thickness, microstructure and texture affect the magnetic properties as well as their polarization and frequency dependence. These structural features represent possibilities to actively alter the magnetic properties, e.g., magnetization curve, magnetic loss or frequency dependence. This paper studies the influence of production and processing on the resulting magnetic properties of a 2.4 wt% Si ...

Effects by the microstructure after hot and cold rolling on the texture and grain size after final annealing of ferritic non-oriented FeSi electrical steel

The magnetic properties of fully processed non-oriented FeSi electrical steel are characterized by their magnetization behavior and specific magnetic losses. The magnetic properties are determined by the texture and microstructure. Less gamma fiber intensity and a high intensity of preferable texture components, especially cube fiber texture, are desirable to obtain an excellent magnetizing behavior. Furthermore, large grain sizes are necessary to reach low values of the specific magnetic losses. The fabrication route of the fully processed non-oriented electrical steels comprises a heavy cold rolling of the hot rolled material before final annealing. To fulfill the requirements on large grain size for low loss materials, grain growth, which appears after complete recrystallization, plays an important role. In this paper we will analyze the influence of different microstructures of the hot strip and the resulting microstructure after cold rolling on the appearance of recrystallization and grain growth aft...

Hot rolling simulation for non-oriented electrical steel

For improving material properties, a fundamental knowledge of all processing steps is necessary. Non-oriented electrical steels are characterized by low losses and a high permeability in the final application. To achieve high grades, every processing step needs to be coordinated with the previous and subsequent one. Simulation tools are useful to harmonize these steps. Experimental investigation had shown, that a heterogeneous material flow and microstructure evolution is a key feature for bcc Iron-Silicon alloys. Therefor hot rolling of non-oriented electrical steel with a silicon content of 2.4 wt.% is simulated by the software LaySimS that allows a fast investigation of heterogeneous deformation stated during rolling. In comparison to experimental rolling trials on a semi-continuous rolling mill the area of validity is predicted and shown. The focus of a comparison between experiment and simulations is put to the microstructure after hot rolling.

Influence of Hot Rolling Condition on the Final Microstructure of Non-Oriented Electrical Steel Fe-3.2 wt.% Si

In this paper the microstructure evolution of an iron-silicon alloy with 3.2 wt.% silicon throughout the manufacturing stages hot rolling, cold rolling and annealing is presented. Starting with a 35 mm thick feedstock, which was hot rolled to 1 mm, with different cooling conditions, the material was cold rolled to a final thickness of 0.3 mm and final annealed under same conditions to show the influence of the hot rolling on the texture and microstructure of the final annealed material.

Frequency Dependence of Magnetization Behavior for FeSi Materials With Different Thickness

Electrical steels with lower thickness become more and more important to realize electrical machines with high nominal frequency due to high number of the poles and to provide higher power at a given volume of the electrical machine. For application at higher frequencies the dynamic magnetization processes have to be analyzed. In the paper the experimental data for frequency dependence of the magnetization curves, the coercive force, the permeability, and of the magnetic losses for nonoriented electrical steels with thicknesses in the range of 0.10 mm up to 0.50 mm will be reported. For thin electrical steels a different character of the dynamic magnetization behavior at increasing frequency of the applied external field compared to thicker materials is observed. This is attributed to differences in the number of moving walls.