294 IEEE TRANSACTIONS ON MAGNETICS, VOL. 46, NO. 2, FEBRUARY 2010 Barkhausen Noise and Magnetic Properties of Plastically Deformed Silicon Steels Ricardo Baiotto , Gunther Gerhardt , Marcos Fukuhara , Taeko Yonamine ,and Frank P. Missell Universidade de Caxias do Sul, Caxias do Sul, RS 95070-560 Brazil Divisão de Metrologia de Materiais, INMETRO, Duque de Caxias, RJ 25250-020 Brazil We present Barkhausen noise and magnetic measurements on two fully processed, nonoriented electrical steels which had been cold- rolled to thickness reductions of up to 60%. Both coercive field and hysteresis loss show an almost linear increase with thickness reduction up to the highest deformations. These changes are almost fully reversed after vacuum annealing for 2 h at 760 . The hysteresis loss can be conveniently subdivided into high and low induction components as suggested by recent modelling. Electron back-scatter diffraction (EBSD) shows no texture change during initial phases of cold-rolling. Barkhausen noise measurements were obtained on both cold-rolled and annealed samples. The undeformed material shows a Barkhausen signature consisting of two small peaks which coalesce into one peak upon plastic deformation and thereafter grow steadily. Annealing the material brings back the two-peaked sig- nature. These results are discussed and hypotheses are presented for the behavior of the Barkhausen noise. Index Terms—Barkhausen noise, coercive field, EBSD, hysteresis loss, plastic deformation, silicon steel. I. INTRODUCTION P LASTIC deformation has a marked effect on the mag- netic properties of silicon steels used for electrical pur- poses, not only on the hysteresis loss and coercive field, but also on Barkhausen noise emission [1]. This is a very important consideration for industry since the performance of steel sheets for motors will be affected by the strains introduced during stamping [2]. Plastic deformation increases the dislocation den- sity which affects domain wall motion and pinning and also pro- duces residual stress. A number of authors have considered the effect of plastic deformation on the magnetic properties of sil- icon steel, frequently focusing on the sharp increase in both co- ercive field and hysteresis loss at low deformations [3]–[6]. Here we consider very large deformations. In this work we present Barkhausen noise and magnetic measurements on two fully pro- cessed, nonoriented electrical steels which had been cold-rolled to thickness reductions of up to 60%. II. EXPERIMENT The samples used in this work were fully processed, non- oriented commercial electrical steels, kindly provided by ArcelorMittal. Samples were cut along the rolling direction (RD) with dimensions . The compositions of the samples are given in Table I below. Samples were cold rolled to a final thickness and the thick- ness reduction was calculated as , where is the ini- tial thickness (0.5 mm) of the undeformed material. After cold rolling, the samples were cut in half and one half underwent an anneal (760 , 2 h) followed by a slow cooling in a vacuum furnace. Both the cold rolling and the heat treatment were per- Manuscript received June 18, 2009; revised August 31, 2009; accepted September 15, 2009. Current version published January 20, 2010. Corre- sponding author: F. P. Missell (e-mail: fmissell@yahoo.com; fpmissel@ucs.br). Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TMAG.2009.2032859 TABLE I PHYSICAL PROPERTIES OF SAMPLES Fig. 1. Loss separation for unannealed E230 as a function of thickness reduc- tion. Total loss (60 Hz/1.5 T) , hysteresis loss , classical loss , and anomalous loss are shown. formed at the Instituto de Pesquisas Tecnológicas do Estado de São Paulo (IPT-SP). Hysteresis curves for the samples were obtained at 60 Hz/1.5 T using a Brockhaus MPG-100D system equipped with a single sheet tester (SST). A fluxmeter allowed measure- ments in static fields. Loss components were determined as a function of frequency as described in [7]. Fig. 1 below shows loss components versus thickness reduction for unannealed E230. Crystallographic texture measurements were made using electron back-scatter diffraction (EBSD) with a FEI Quanta 200 scanning electron microscope equipped with an EBSD system from TexSEM Laboratories (TSL). Samples surfaces were prepared using standard metallographic techniques. After EBSD measurements, grain sizes (GS) were determined on the same samples using the intercept method. The grain sizes (GS) for the undeformed samples are given in Table I. 0018-9464/$26.00 © 2010 IEEE