Sang Yun Cha

Stabilization and destabilization of domain wall positions in FeSi polycrystals using magnetic annealing effects

The effect of variation of magnetic annealing conditions on the properties of grain-oriented Fe-3%Si steels was investigated. It was shown that during magnetic annealing with special magnetizing conditions (in the B-range, corresponding to the stability of a large number of 90°-supplementary domains), the special magnetic structure is stabilized. This state is characterized by the increase of the sample magnetostriction in low and high fields as well as under compression, demonstrating the increased contribution of 90°-domain wall displacements and the magnetic domain structure rearrangement. The initial material state may be recovered using magnetic reannealing in the AC field by means of destabilization of induced changes in structure. Magnetic annealing in high DC fields yields an increase of preferred alignment of magnetic domains along the rolling direction and a pronounced magnetostriction decrease.

Study of pinning conditions, magnetic domain structure and magnetic properties of laser-scribed 3%Si-steels

Commercial grain-oriented Si-steels have been studied using magnetostriction and magnetic properties, analysis of magnetic domain structure and complex susceptibility spectra. It is shown that the analysis of modifications in the complex susceptibility spectra of laser-scribed samples can be useful for revealing of optimal technological parameters for the laser treatment of industrial Si-steels.

Effects of uniaxial stress on the magnetic properties of laser scribed grain oriented 3.2% Si steel

Effects of laser scribing on the magnetic properties of commercial grain-oriented 3.2% Si steels were investigated. Laser scribing was shown to play a significant role in reducing the core loss of tension-coated grainoriented (GO) Si steels. The reduction ratio of the core loss was dependent on the applied strees conditions and orientation of magnetic domains. Longitudinal tensile stress contributes to the increase of magnetic flux density. Laser scribing contributes to the redistribution of magnetic domains and creates 90° magnetic domains. GO Si steel is described by negative values of magnetostriction. Laser scribing results in magnetostriction positive values whereas application of tensile stress causes negative magnetostriction.

Study of Magnetic Annealing on Magnetostriction in Grain-Oriented 3.2 % Si Steels

The effects of magnetic annealing on a magnetiostriction in commercial grain-oriented 3.2 at.% Si steels were investigated. A combined (constant+strong pulsed) magnetic field during the magnetic annealing played a significant role in reducing the magnetostriction. The reduction ratio in magnetostriction was greatly dependent on surface conditions such as whether it was a bare metallic, tension coated and laser-scribed surface for grain-oriented electrical steels. For all three samples, the effect of the magnetic annealing on reduction in maganetostriction is more clearly observed in the compressive stress rather than in the tensile stress region.