科研之友
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摘要
At present, the quality of commercial non-oriented electrical steels is improved mainly by optimizing deformation and recrystallization textures, but the most desirable {100} texture for the magnetic properties of sheets is normally no more than 20% in volume fraction. Through alpha ->gamma ->alpha transformation, however, the percentage of {100} texture can be up to 50%, even as high as 80% or more. The characteristics of transformation microstructure in ultra-low carbon non-oriented electrical steel are basically revealed in this work, and the formation mechanisms are analyzed and discussed. The cold-rolled sheets of electrical steels are heated in gamma single phase region, alpha ->gamma ->alpha transformation occurs in hydrogen and nitrogen atmosphere, respectively. The results indicate that strong {100} texture with monolayer pancake grains is developed in hydrogen, and the size of {100} oriented grains reaches more than 1 mm; whereas near {100} and {110} textured columnar grains are formed at the surface layer of the sheets in nitrogen, and the equal-axed grains with {111} and {114} textures in the center layer are obtained finally. Sigma 3 grain boundaries generally appear in the transformation microstructure where grain orientations are preferred, and its formation mechanism is closely related to K-S relationship which is followed during variant selection induced by surface-effect. There is an approximate linear orientation gradient in the columnar grains at the surface of the sheet annealed in nitrogen, and this phenomenon should be resulted from the accumulation of transformation strain induced by the suppression of the growth of surface grains with gamma ->alpha transformation along the normal direction.
- 出版日期2017-1
- 单位北京科技大学
