Stress Dependence of Magnetic Properties in Non-oriented Electrical Steel Sheets

Abstract

This paper discusses the stress dependence of magnetizing properties in non-oriented electrical steel sheets (NO). Compression stresses deteriorate the magnetic properties at low flux density, but improve them at high flux density, where magnetization rotations are induced. Tensile stresses reduce magnetizing fields at low flux density, but increase them at high flux density. The stress dependence of NO is affected by the exciting direction, as the rolling direction of NO is easy to magnetize and sensitive to stresses. High-grade types of NO (50A290, etc), which have high Si content and large crystalline grains, are more sensitive to stresses than low grades (50A1300, etc), and the magnetizing fields of high grades at high compression are higher than those of low grades. This stress dependence may depend on magnetization behaviors (domain wall displacement and magnetization rotation) and magnetostriction. Domain wall displacement mainly occurs at lower flux density, and in this case tensile stresses improve magnetic properties and compression deteriorate them because magnetic domains orient the magnetization to <100> and λ100 is positive. However, magnetizations rotate to exciting directions at high flux densities, with the result that the <111> component of magnetization is induced, and in this case compression improves the magnetizing properties, because λ111 is negative, whereas tensile stress deteriorates them. Therefore, stress dependences may be modeled by magnetization behaviors and magnetostriction, and analysis of the magnetic properties using this model of stress dependence may improve NO steels and their applications.