Papers by Keyword: Grain Oriented Silicon Steel

Abstract: A microsecond pulsed laser beam was used to local magnetic domain modification of electrical grain oriented silicon steel. It was carried out using three different laser pulse regimes: a single pulse laser regime, a multipulse laser regime and a multipulse laser regime with modulation of laser pulses. The laser processing variables were pulse energy and and number of pulses. The samples were tested for nanohardness and coercivity before and after laser treatment. Light optical microscopy, scanning electron microscopy and magnetic force microscopy were used to observe the cross-sectional profile, surface of the samples, and magnetic domain visualization, respectively. The local laser treatment of grain oriented silicon steel surface has been studied in terms of its influence on the magnetic domains and coercivity. It was found that laser-modified samples showed coercivity improvement in comparison to the non-treated samples. The most significant improvement in coercivity was obtained in the modulated multipulse regime and negligible improvement in the single pulse laser regime. Three main effects responsible for the observed improvement were identified, namely: magnetic domain refinement, influence of number of laser pulses and shape of laser HAZ profile. The present work highlights on differences in the magnetic domain structure, microstructure of the laser modified material and basic electromagnetic and mechanical properties. In present study, the pulse laser surface processing was presented as a useful energy efficient alternative to other techniques e.g. mechanical scribing, electrical discharge scribing, plasma jet scribing, etc. The refined magnetic domains in electrosteels are responsible for the observed low coercivity, which indicates perspective application of the investigated laser modified steels in the power transformer cores with lower core losses.

Abstract: In order to find out the optimum thermodynamic conditions for hot metal dephosphorization and predict phosphorus content after demanganization pretreatment, thermodynamic equilibrium experiments between CaO-FetO-SiO2-MnO-P2O5 slag and silver/solid iron were carried out in an iron crucible at different temperature under pure argon atmosphere in an electric resistant furnace. The results indicate that phosphorus distribution ratios increase with an increase of basicity in the slag at the experiment temperature, and then they decrease with an increase of basicity at 1573K and 1623K. The phosphorus distribution ratios decrease with an increase of FetO content in the slag at 1573K, while they increase with an increase of FetO content in the slag and then decrease with an increase of FetO content in the slag at 1623K. The results indicate that the maximum phosphorus distribution ratio between slag and hot metal is 92.4 when basicity of the slag is 1.7 and FetO content in slag is 49.75 mass% at 1623K, and the correspondent phosphorus content in the carbon saturated iron is 0.019mass%. Dephosphorization is easier under low temperature. The equilibrium quotient of phosphorus obtained in the present work is formulated as a function of slag compositions and temperature using the multiple regression method which is used to predict phosphorus content equilibrium with the demanganization slag and optimum conditions needed for ideal phosphorus contents in demanganization pretreatment.

Abstract: A laser is often considered to scribe the steel surfaces after cold-rolling and annealing to reduce the energy losses associated with hysteresis and eddy currents. In order to maximize the loss reduction of this process, the laser scribing technics was investigated in details. In this work, three laser scribing parameters including pulse energy, scanning velocity and scribing spacing, which are highly related to the loss reduction, were selected for the study. A L9(34) orthogonal experiment was designed and carried out by an Nd:Yag laser marking machine. The results indicate that the subsequence of significance of the three factors on core loss reduction is as follows: pulse energy, scribing spacing and scanning velocity. And an optimized combination of parameters is obtained by range method.

Abstract: The texture distribution and development of grain oriented silicon steel with different production stages have been investigated by electron backscatter diffraction technique (EBSD). The results indicated that below the surface the intensity of {001}<110> of α-fiber was strongest with a amount of {110}<001> texture and γ-fiber. After first cold rolling and normalizing, in the corresponding position the {110}<001> texture and γ-fiber appeared again. The {110}<001> grains and γ-fiber after decarb-annealing was helpful to accelerate the abnormal growth of second grain nucleation.

Abstract: The local-area analyses of the primary recrystallization sheets were carried out in Fe-3%Si to explain the reason why only Goss appears during the secondary recrystallization. It was found in the present study that Goss grains have the higher Σ9 frequency in their nearest neighbors than {311}<011> grains, both of which were attached to the neighbors having the texture with high Σ9 frequency to the texture of the matrix. Another analysis showed that Σ1 and Σ3 frequencies were higher around {311}<011> grains than around Goss. It is concluded that Goss grains possess the satisfactory criteria to be the secondary recrystallization nuclei from the following viewpoints of high Σ9 frequency and low Σ1 and Σ3 frequencies.

Abstract: 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.