Papers by Keyword: Grain Oriented Electrical Steel

Abstract: A Fe-3wt% Si strip was produced using a vertical type twin-roll casting process. Sub-grains with an inhomogeneous distribution through the thickness direction were firstly observed in the as-cast strip. It was found that the surface layer was characterized by columnar grains containing lineage sub-grains, the subsurface layer was dominated by numerous polygonal sub-grains inside columnar grains or fine equiaxed grains, and the center layer was composed of coarse equiaxed grains without sub-grains. In addition, the sub-grain boundaries provided additional nucleation sites for precipitates and the nanoscale MnS particles were successfully obtained. Moreover, the average size of MnS precipitates in the surface layer was smaller than that in the subsurface layer. The inhomogeneous distributions of sub-grains and precipitates can be attributed to the large temperature gradient through the thickness direction during the strip casting process.

Abstract: Grain oriented electrical steels should have low core loss and high magnetic flux density. These properties are closely related with sharpness of {110} texture after secondary recrystallization. This Goss texture develops by abnormal grain growth during secondary recrystallization annealing. Based on experimental results, a general suggestion which estimates the magnetic properties after secondary recrystallization from a primary recrystallized texture can be made. For a material to have better magnetic properties after secondary recrystallization, its primary recrystallized texture should have not only larger number of ideal Goss grains, but also lower frequency of low angle grain boundary around those Goss grains.

Abstract: The effects of inter-pass ageing temperature during cold rolling on structure, magnetic properties and mechanical properties of high permeability grain oriented electrical steel was studied. The samples were processed in a single-stage cold rolling to 0.27 mm thickness, with 88 % reduction, without and with inter-pass ageing treatment in order to determine the magnetic properties. To determine the changes in mechanical properties due to strain ageing, the samples underwent overlapped ageing, after pre-strain by rolling, under the same conditions of inter-pass ageing and then were subjected to tensile test. The effect of strain ageing was more pronounced in the thickness of 0.7 mm and the largest variation in yield strength was at 200°C in all evaluated thicknesses. At this temperature the largest amount of {110} orientation after primary recrystallization was also observed, as well as the lowest final grain size and consequently the best results of core loss. The magnetic induction had almost no alterations.

Abstract: The possible mechanisms concerning abnormal growth of Goss grains in grain oriented electrical steels were investigated. The density of inhibitor particles near sheet surface, where the Goss grains located, was lower than that in center layer before secondary recrystallization, and the grains near surface could grow more easily because of reduced pinning effect. Few Goss grains could survive the growth competition and reach the sheet surface, after which the inhibitor particles inside the Goss grains coarsened slower. The phenomenon resulted in easy growth of the Goss grains at the expense of smaller neighboring grains while they could hardly be consumed by larger neighboring grains during the high temperature secondary recrystallization. Very large final size of the Goss grains was then obtained. The mechanisms were discussed based on the hot rolling characteristics and the elastic anisotropy of the ferrite matrix.

Abstract: Desirable magnetic properties for grain oriented electrical steels are low core loss and high magnetic flux density. These properties are closely related with sharpness of {110} texture. This Goss texture develops by abnormal grain growth during secondary recrystallization annealing. Based on experimental results, a general suggestion which estimates the magnetic properties after completion of secondary recrystallization from a primary recrystallized texture can be proposed. For a material to have better magnetic properties after completion of secondary recrystallization, it should have a primary recrystallized texture in which there are not only large number of ideal Goss grains, but also lower frequency of low angle grain boundary around those Goss grains.

Abstract: The Bi_0.5Na_0.5TiO₃-xwt%BaTiO₃ compound ceramics were prepared. The influence of different BaTiO3 content on structure was evaluated by scanning electron microscopy and X-ray diffraction analysis. The results show oriented is induced by plate-like BaTiO₃ template. Signficant improvement of the piezoelectric (d33 = 112 pC/N) and dielectric properties ( max ≈ 5500) was observed. The improvement was attested to the apparent alignment of the BaTiO₃ templates and grain oriented growth.

Abstract: The precipitation behaviors of fine MnS and other second phase particles in hot band, decarburized sheet and 875 oC annealed sheet before secondary recrystallization of conventional grain oriented electrical steel were investigated. It is indicated that the small particles as inhibitors would dissolve in the matrix during cold rolling, and precipitate again in following annealing treatment. The particles inside grains would keep retarding the grain boundary migration. It was found that the particle densities in all grains were quite different before initiation of secondary recrystallization and might be grain orientation dependent, in which Goss grains showed higher particle density. It is expected that the grain boundaries would move towards the grains with lower particle density more easily and promote the rapid growth of Goss grains. The reason for difference of particle densities in different grains is quite complicated. The influence of possible different dislocation densities and the different precipitation behaviors of second phase particles are mentioned.

Abstract: The compact strip processing technology and the technologies for conventional grain oriented electrical steels were used to process the low cost grain-oriented electrical steel successfully, in which the reheating temperature for hot rolling was about 1150 oC, and strong Goss texture was obtained after the secondary recrystallization. It is indicated that the density of inhibitor particles produced under the condition of low temperature hot rolling was high enough to induce the necessary secondary recrystallization during final annealing, so that many Goss grains could grow. The mis-orientations of Goss grains to the recrystallization matrix were calculated and observed. High angle boundaries enveloped frequently Goss grains, while the growth of other grains would have the possibility to meet low angle boundaries or low mobile boundaries. Goss grains neighboring larger size grains might be protected by the further precipitation of inhibitor particles in high angel boundaries during the temperature rising stage of the secondary recrystallization and survived somehow after the growth competition.

Abstract: Recrystallization texture in grain oriented silicon steel at different annealing temperature is investigated. Normalized x-ray intensities of various orientation components observed in Orientation Distribution Function are used for comparison. The computed CSL boundary distributions about Goss component with annealing condition were calculated. The misorientation angle distribution is also measured in order to find the importance of high-energy boundary with misorientation 20~45° range for the secondary recrystallization of Goss grain. From the analysis of CSL boundary distribution and misorienation angle distribution, the distribution of CSL boundaries does not evidently show any preferred difference between Goss and other texture components. Whereas, the misorientation angle analysis shows that the number of 20°~45° misoriented boundaries is higher around the Goss grains than around other texture components.