Investigation of the magnetic properties of Si-gradient steel sheet by comparison with 6.5%Si steel sheet

T Hiratani,S Yoshizaki,K Senda,Y Zaizen,Y Oda

doi:10.1063/1.5007190

Abstract

In this study, we investigated the magnetic properties of Si-gradient steel sheet produced by CVD (chemical vapor deposition) siliconizing process, comparing with 6.5% Si steel sheet. The Si-gradient steel sheet having silicon concentration gradient in the thickness direction, has larger hysteresis loss and smaller eddy current loss than the 6.5% Si steel sheet. In such a loss configuration, the iron loss of the Si-gradient steel sheet becomes lower than that of the 6.5% Si steel sheet at high frequencies. The experiment suggests that tensile stress is formed at the surface layer and compressive stress is formed at the inner layer in the Si gradient steel sheet. The magnetic anisotropy is induced by the internal stress and it is considered to affect the magnetization behavior of the Si-gradient steel sheet. The small eddy current loss of Si-gradient steel sheet can be explained as an effect of magnetic flux concentration on the surface layer.

Highlights

Si is one of the most effective elements for improving the magnetic properties of steel
The Si-gradient steel sheet shows lower iron loss than 6.5% Si steel sheet despite the average Si content being less than 6.5%
We investigated the magnetic properties of Si gradient steel sheet compared with 6.5% Si steel sheet and discussed the magnetization mechanism

Summary

Introduction

Si is one of the most effective elements for improving the magnetic properties of steel. Resistivity of the steel increases with Si content. The high resistivity is helpful to reduce eddy current losses caused by AC magnetization. When the Si content is further increased to 6.5%, the saturation magnetostriction falling to 0 and the permeability becomes maximal. When the Si content exceeds 4%, the ductility of the steel significantly decreases, making it difficult to produce a thin steel sheet by ordinary rolling process. Industrial production of 6.5%Si steel sheet became possible by CVD siliconizing process.1,2 6.5% Si steel sheet is mainly used as core material effective for low noise transformer and reactor at audible frequency.[3]

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