Influence of Process Parameters on Grain Size and Texture Evolution of Fe-3.2 wt.-% Si Non-Oriented Electrical Steels.

Xuefei Wei,Johannes Lohmar,Nora Leuning,Kay Hameyer,Anett Stöcker,Sandra Korte-Kerzel,Gerhard Hirt,Alexander Krämer,Martin Heller,Rudolf Kawalla,Lucas Böhm,Wolfram Volk

doi:10.3390/ma14226822

Abstract

The magnetic properties of non-oriented electrical steel, widely used in electric machines, are closely related to the grain size and texture of the material. How to control the evolution of grain size and texture through processing in order to improve the magnetic properties is the research focus of this article. Therefore, the complete process chain of a non-oriented electrical steel with 3.2 wt.-% Si was studied with regard to hot rolling, cold rolling, and final annealing on laboratory scale. Through a comprehensive analysis of the process chain, the influence of important process parameters on the grain size and texture evolution as well as the magnetic properties was determined. It was found that furnace cooling after the last hot rolling pass led to a fully recrystallized grain structure with the favorable ND-rotated-cube component, and a large portion of this component was retained in the thin strip after cold rolling, resulting in a texture with a low γ-fiber and a high ND-cube component after final annealing at moderate to high temperatures. These promising results on a laboratory scale can be regarded as an effective way to control the processing on an industrial scale, to finally tailor the magnetic properties of non-oriented electrical steel according to their final application.

Highlights

Non-oriented (NO) electrical steel is widely used to make stators and rotors of electric machines like generators and motors
For each of these three steps, experimental investigations were carried out to identify the influence of the process parameters introduced in detail above on both the microstructure in terms of grain size distribution and the texture in terms of orientation distribution function (ODF)
A low finishing temperature in combination with water quenching after hot rolling led to a deformed state with small grains near the surface and a banded structure with flat elongated grains in the mid layer, whereas a furnace cooling after hot rolling resulted in a fully recrystallized, more homogeneous microstructure across the strip thickness with a mean grain size of

Summary

Introduction

Non-oriented (NO) electrical steel is widely used to make stators and rotors of electric machines like generators and motors. Their overall efficiency and performance depend strongly on the quality of the NO electrical steel. High quality NO electrical steel provides good magnetic properties, especially easy magnetization and low magnetic losses. These magnetic properties are inextricably linked to the grain size and crystallographic texture of the material. I.e., center lines of continuous orientation tubes in Euler space are usually used to describe these characteristic texture components [2]. To quantify the magnetic quality of a texture, Kestens et al [6] proposed the A-parameter, where the angle Aθ (g) is the minimum angle

Methods

Results

Discussion

Conclusion