Si-Fe Strips Research Articles

Control of the number of {110} grains and magnetic induction in inhibitor-free 3% Si–Fe strips

After annealing with various heating rates, all the strips containing 58 ppm sulfur consisted of {110} grains, showing a magnetic induction over 1.95 T. Magnetic induction in the strips containing 11 ppm sulfur, on the contrary, varied from 1.98 to 1.48 T, depending on the additional amount of {100} and {111} grains. Direct isothermal annealing and a heating rate of 25 °C/h were advantageous for obtaining final {110} texture. These results are explained in terms of the segregation kinetics of sulfur affected by heating rate and the grain boundary pinning effect of the segregated sulfur.

Optimal Bulk Content of Sulfur for High Magnetic Induction in Inhibitor-Free 3% Si-Fe Strips

Effects of bulk content of sulfur on final texture and magnetic induction have been investigated in 3% silicon iron strips. Within the tested range of sulfur content from 11 to 92 ppm, too high or low sulfur contents resulted in a poor magnetic induction arising from no or a limited {110} texture. A weak {110} texture at a high sulfur content is due to the prolonged time period of {100} or {111} grain growth. Despite the shortened time period of selective growth of {100} or {111} grains, also the weak {110} texture at a low sulfur content is probably attributed to a weak grain boundary pinning effect of the weakly segregated sulfur. A moderate sulfur content provides an appropriate pinning effect enough to suppress {100} or {111} selective growth, finally resulting in a sharp {110} texture.

Pre-annealing and magnetic induction in inhibitor-free 3% Si–Fe strips

Effects of pre-annealing and hydrogen flow rate on final texture and magnetic induction have been investigated in inhibitor-free 100 μm thick 3% Si–Fe strips containing 18 ppm sulfur. Without any pre-annealing, the strip showed a low magnetic induction, due to various {1 1 0}, {1 0 0} and {1 1 1} final texture components. The number and the area fraction of {1 1 0} grains increased with increasing pre-annealing temperature and hydrogen flow rate. A pre-annealing temperature range that results in the sharp {1 1 0} 〈0 0 1〉 texture is observed, depending on the hydrogen flow rate.

Effect of preannealing on final texture and magnetic induction in thin-gauged 3% Si–Fe strips containing 0.1% Mn and 0.011% S

In 0.1mm thick 3% Si–Fe strips containing 0.1% manganese and 0.011% sulfur, the preannealed strips were composed of {110} grains after final annealing at 1200°C, while the other strips without preannealing consisted of {100} or {111} grains. This is due to the difference in surface-energy-induced selective growth kinetics in which the main governing factor is probably by the primary grain size. In the preannealed strip with a higher final reduction, the relatively smaller grain size effect produced the decrease in total number of the {110} grains and thus the sharper {110}⟨001⟩ final texture favorable for the higher magnetic induction.

Nucleation, selective growth, and magnetic induction in 3% Si-Fe strips

It is shown that nucleation, selective growth, and magnetic induction are directly influenced by heating rate and strip thickness in 3% Si-Fe alloy strips. The (110) grains were easier to survive in thinner strips than in thicker strips. The [001] direction of (110) grains became closer to the rolling direction with increasing heating rate. These results are explained in terms of the surface segregation kinetics of sulfur governed by the heating rate and strip thickness. The present paper shows that thinner strips with a relatively faster heating rate are more advantageous for obtaining a higher magnetic induction that results from the final (110)[001] texture.

Control of nucleation behavior and high magnetic induction in thin-gauged 3% Si–Fe strips

Even in thin-gauged 3% Si–Fe strips with the same final thickness reduction, the strong {110}〈001〉 Goss component at the cold-rolled strip surfaces becomes the {110}〈001〉 texture after final annealing, which results in a magnetic induction (B10, Tesla) higher than 1.9 T. On the other hand, the strips with the {110}〈uvw〉 component deviating from the Goss component show a low magnetic induction (B10, Tesla) of about 1.60 T which results from the final {110}〈uvw〉 texture. The strong dependence of final texture and magnetic induction on the cold-rolling texture at the surfaces of the strip is due to the intrinsic characteristic of diffusionless nucleation that is followed by the surface-energy-induced selective grain growth.

Effects of heating rate and surface oxidation on magnetic induction of 3% Si–Fe strip

The effects of heating rate and surface oxidation on magnetic induction of thin-gauged 3% Si–Fe strips have been investigated. Magnetic induction increased with increasing final annealing temperature. Before and after 1150 °C, the planar orientation of grains shifted from (100)[011] to (110)[001], resulting in magnetic induction higher than 1.90 T. Magnetic induction after final annealing was higher in case of a faster heating rate. This is because enough time for growth of (110) grains is given in the case. Irrespective of transient annealing temperature, magnetic induction after final annealing was mostly higher than 1.90 T. A maximum, 1.97 T, was obtained at a transient annealing temperature of 800 °C. This is because iron oxide formed at 800 °C inhibited the surface-energy-induced selective growth of (100)[011] grains during heating up to 1200 °C.

Tertiary recrystallization and magnetic induction under various annealing atmospheres in thin-gauged 3% Si–Fe strip

Surface-energy-induced secondary or tertiary recrystallization by grains with a specific surface plane can be freely governed in thin-gauged 3% Si–Fe strips by controlling the bulk content of sulfur and annealing atmosphere. During a vacuum or hydrogen annealing process, a convex profile in segregated-sulfur concentration is formed due to evaporation or desorption of segregated sulfur as a hydrogen sulfide, corresponding to a trough in magnetic induction. High magnetic induction is obtained after the annealing treatments. Final annealing under an argon atmosphere caused a saturation in segregated-sulfur concentration with annealing time. Under this extremely high segregated sulfur, grains of high index crystal plane including {111} continued to grow, resulting in low magnetic induction.

Study on Surface Magnetic Domain Structure of Thin-Gauged 3%Si-Fe Strips Using Scanning Electron Microscope with Polarization Analyzer

Due to the important soft magnetic characteristics, 3%Si-Fe strips have been extensively studied and is currently used as core material of distribution and power transformers where energy losses during magnetization are of critical concern. It is well known that the energy loss decreases significantly with decreasing thickness of 3%Si-Fe strips. (110)[001] Goss texture in thin-gauged 3%Si-Fe strips is developed through a tertiary recrystallization process which is induced by the difference in surface energy of (110) and other grains. To reduce the energy losses of 3%Si-Fe strips, the domain modification by the application of uniaxial tensile stress, mechanical scribing and laser scribing has been developed, but there are few studies on the domain structure of the thin-gauged Si-Fe strips. In this study, the magnetic property, B{sub 10}(T), is controlled by changing the reduction ratio per pass are (hereafter, reduction rate) in cold rolling 3%Si-Fe plates, and surface magnetic domain structures each are imaged using scanning electron microscope with polarization analyzer (SEMPA).

Eddy current losses and number of domain walls with respect to total number of layers for very thin 3% Si-Fe strip-wound cores

The relation between the domain wall motion and the eddy current losses of very thin (110)[001] 3% Si-Fe strip-wound cores were investigated. The measured eddy current losses were larger than those estimated using a modified Pry and Bean model in the frequency region 50–500 Hz. It is known that the domain walls of thick (110)[001] 3% Si-Fe strips move nonuniformly in the low-frequency range (0.1–100 Hz), but this frequency range is lower than that usually used for very thin strips. By measuring the flux voltage in every layer, we found that the voltage waveforms were not sinusoidal, even if the secondary voltage waveform of the core was sinusoidal, and the magnitude of the voltage in each layer was not uniform. These results indicate that the domain wall motion of very thin strips is not uniform, even at 50–500 Hz. The nonuniformity of the domain wall motion makes the eddy current losses larger than those estimated by means of the modified Pry and Bean model.

Analysis of inclusions in cold-rolled n.o. Si-Fe strips

In this work the effect of the inclusion structure to the core loss of n.o. electrical steels were investigated. Si-Fe sheet samples were analyzed by scanning and diffraction electron microscopy. It was shown, that the large ( > 0.5 μm) and the very fine (< 0.05 μm) precipitates are less harmful to the magnetic properties than the 0.05-0.5 μm sized ones.

Barkhausen noise of 3% Si-Fe strips after plastic deformation

Grain-oriented 3% Si-Fe strips were plastically strained up to \epsilon = 3 %. The frequency spectrum E(f) of the Barkhausen noise was measured. From E(O) a mean Barkhausen volume v eff is calculated. The noise and v eff are diminished after plastic deformation mainly already in the region \epsilon %, where the coercive field remains still constant, v eff is related to a mean irreversible susceptibility, which is mainly determined by the hysteresis loop. By measurements of the correlation of the flux changes along the specimen a mean length of the Barkhausen volumes was obtained. Its diminution mainly causes the diminution of v eff . The connection of the results with changes of the domain and dislocation structure is discussed.