Estimation of the Damaged Zone Width due to Mechanical Cutting on High Quality Non-Oriented Steels

Abstract

In electrical machine production, the mechanical cutting procedure induces plastic deformation and mechanical stresses, which are directly linked to the magnetic properties’ degradation. In spite that the non-oriented electrical steel has a small magnetocrystalline anisotropy, the influence of the easy and hard magnetization axes on the magnetic permeability and energy losses is important. In this study we present a mathematical model, used for the damaged zone width estimation that results from the mechanical punching procedure. Through this technological cutting method NO20 non-oriented electrical steel strips of 300 mm × 30 mm were prepared, being cut parallel (RD) and normal (TD) to the rolling direction. The Epstein standard sample 30 mm in width was reconstructed, by putting together strips having their width in an interval between 5 mm and 30 mm. These samples were assessed utilizing a laboratory Single Strip Tester (SST) for frequency ranging from 3 Hz to 400 Hz, at J p = 1 T (peak magnetic polarization value). Using the statistical theory of losses (STL) total energy losses were decomposed into hysteresis, classical and excess losses, and their variation was investigated as a dependence of the strip width.