Grain Size Influence on the Magnetic Property Deterioration of Blanked Non-Oriented Electrical Steels

Abstract

Non-oriented electrical steel sheets are applied as a core material in rotors and stators of electric machines in order to guide and magnify their magnetic flux density. Their contouring is often realized in a blanking process step, which results in plastic deformation of the cut edges and thus deteriorates the magnetic properties of the base material. This work evaluates the influence of the material’s grain size on its iron losses after the blanking process. Samples for the single sheet test were blanked at different cutting clearances (15 µm–70 µm) from sheets with identical chemical composition (3.2 wt.% Si) but varying average grain size (28 µm–210 µm) and thickness (0.25 mm and 0.5 mm). Additionally, in situ measurements of blanking force and punch travel were carried out. Results show that blanking-related iron losses either increase for 0.25 mm thick sheets or decrease for 0.5 mm thick sheets with increasing grain size. Although this is partly in contradiction to previous research, it can be explained by the interplay of dislocation annihilation and transgranular fracturing. The paper thus contributes to a deeper understanding of the blanking process of coarse-grained, thin electrical steel sheets.

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

“…Thereby, every publication focuses on a different aspect of this material. Two papers revolve around processing and its influence on microstructure, texture and magnetic properties [ 4 , 5 ]; one deals with integrated process simulation [ 6 ] and the last with material design [ 3 ], all drawing heavily on experimental results from the established and advanced methods described and discussed here. In the current paper, we present the key methods for fully characterizing the most important properties of electrical steel.…”

Analysis of the Process and Results of High-Pressure Abrasive Water Jet Multilayer Cutting of Electrical Steel

“…The deviations in the roughness profiles measured for lower cutting speeds (0.972 and 0.774 m/min) have smaller deviations in values than those obtained for higher cutting speeds (2.052 m/min, 1.854 m/min, and 1.29 m/min), for which there are more values above 20 µm, which may cause local defects in the electrical insulating coating on the surface of Figure 6 shows example photos of a bottom part of the sample of sheet metal after cutting, with the cutting edge and the visible area of deformation and local impact of the water-abrasive stream. After the cutting process of electrical steels, the magnetic properties of the product change along with the modification of the material texture in the deformation zone [36][37][38]. It is therefore necessary to minimize the width of this zone.…”

“…Figure 6 shows example photos of a bottom part of the sample of sheet metal after cutting, with the cutting edge and the visible area of deformation and local impact of the water-abrasive stream. After the cutting process of electrical steels, the magnetic properties of the product change along with the modification of the material texture in the deformation zone [36][37][38]. It is therefore necessary to minimize the width of this zone.…”

Numerical modeling of multipoint blanking process of electrical steel

“…The authors of many publications analyze the impact of the process on the quality of products made of electrical steels. The research concerns the analysis of the domain structure of nonoriented electrical steel [1], stress and strain values in the cutting zone [2], microhardness of cut edge, and magnetic properties after process [3][4][5]. According to the conducted analyses, changes in the magnetic properties are strongly influenced by the wear of punching tools.…”