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• Low-finishing-temperature hot rolling and batch annealing result in large grains. • Prior large grains lead to desirable recrystallization microstructure and texture. • A potential processing method to improve magnetic properties is proposed. The grain size prior to cold rolling plays an important role in the microstructural, textural evolution and magnetic properties of non-oriented silicon steel sheets. In this work, we proposed a new way to obtain large grain size before cold rolling and applied it to a 1.0 wt% Si-0.2 wt% Al non-oriented silicon steel, i.e., appropriate low-finishing-temperature hot rolling combined with batch annealing. The grain growth process during batch annealing was investigated using a quasi in-situ electron backscattered diffraction (EBSD) technique. It was demonstrated that significant grain growth took place through a strain-induced boundary migration mechanism. Then a large number of in-grain shear bands were formed in the cold rolled microstructure and could provide nucleation sites for Goss ({1 1 0} 〈0 0 1〉) and λ-fiber (〈0 0 1〉//ND) recrystallized grains, thus resulting in a coarse-grained and homogeneous recrystallization microstructure with weakened γ-fiber (〈1 1 1〉//ND) texture, strengthened Goss and λ-fiber texture. Consequently, superior magnetic properties (B 50 = 1.763 T, P 1.5/50 = 4.30 W/kg) were obtained. For comparison, the conventional processing route without batch annealing was also investigated. A small-grained and inhomogeneous recrystallization microstructure with pronounced γ-fiber texture was produced in the finally annealed sheet, which could significantly deteriorate both the magnetic induction and iron loss. This work provided a new way to enlarge the grains in hot rolled sheets by low temperature batch annealing instead of the conventional high temperature normalization. Thus a new processing route to fabricate low silicon non-oriented electrical steels with high permeability and low iron loss was established. [ABSTRACT FROM AUTHOR]

Secondary recrystallization is responsible for the sharp Goss texture ({110}<001>) of grain-oriented electrical steels. Many investigations have focused on establishing the relations between the sharpness of final Goss textures and primary recrystallization textures measured by the X-ray diffraction. However, the contributions of micro-texture characteristics to secondary recrystallization have not yet been well understood. Here, we report that the grain colonies composed of grains with similar orientations in the primary recrystallization matrix had a particular role on the development of secondary recrystallization via an original tracking experiment. We observe that the γ-grain (<111>//normal direction, ND) colonies facilitate the retention of primary recrystallization matrix grains (≤25µm) having 20-45° disorientation with {110}<001> and relatively large difference in the associated frequency with precise Goss orientation and that having deviation angle of 15°, promoting the abnormal growth of low-deviation-angle Goss grains especially after the onset of secondary recrystallization and leading to sharp final Goss texture. By contrast, the abnormal growth of high-deviation-angle Goss grains may be also promoted after the initiation of secondary recrystallization in case of randomly-distributed γ-grains in primary recrystallization matrix and thus resulted in deteriorated magnetic properties. In this way, we reveal the role of grain colony on secondary recrystallization and the underlying mechanism for the effect of primary recrystallization textures on the sharpness of final Goss texture. We also observe that the formation of grain colonies is mainly related to the initial solidification microstructure, processing route as well as the deformation and recrystallization features of γ-grains. Image, graphical abstract [ABSTRACT FROM AUTHOR]

• Effect of two-stage cold rolling route on microstructure and texture was studied. • Low-reduction cold rolling and intermediate annealing resulted in coarse grains. • γ-Fiber was weakened while λ-fiber and Goss texture were enhanced in final sheet. • Increasing grain size prior to cold rolling led to improved magnetic properties. The 0.5 mm-thick Fe-0.9 wt%Si-0.3 wt%Al non-oriented electrical steel sheets were successfully produced with one-stage and two-stage cold rolling methods. The comparative investigations were conducted on the relationships between the processing routes, microstructures, textures and magnetic properties. This study mainly focused on how to increase the grain sizes prior to cold rolling and its influences on subsequent microstructure and texture evolution. The results showed that the fine microstructure prior to final cold rolling led to the pronounced γ-fiber texture, fine recrystallized grains and deteriorated magnetic properties after final annealing. Nevertheless, by introducing a low-reduction cold rolling and intermediate annealing, coarse grains could be generated prior to the final cold rolling. When the cold rolling reduction was 11%, a relatively homogeneous microstructure composed of fully coarse grains was produced. The increased grain sizes promoted the generation of dense shear bands during final cold rolling, which served as the nucleation sites for λ-grains and Goss grains. This resulted in the improved magnetic properties due to the weakened γ-fiber texture, strengthened λ-fiber texture and Goss texture and increased grain sizes in the final annealed sheets. This work provided a new way to improve the magnetic properties of non-oriented electrical steels by controlling the grain sizes prior to final cold rolling. [ABSTRACT FROM AUTHOR]

The microstructure and texture evolution along the processing was investigated with a particular focus on the secondary recrystallization behavior in a 0.23 mm-thick twin-roll cast grain-oriented electrical steel. A striking feature is that Goss orientation originated during twin-roll casting as a result of shear deformation and it was further enhanced during hot rolling and normalizing. After primary recrystallization annealing, a homogeneous microstructure associated with a sharp γ-fiber texture was produced. During secondary recrystallization annealing, the γ-fiber texture was first strengthened and weakened with increasing temperature prior to the onset of secondary recrystallization. Goss grains always exhibited more 20–45° misoriented boundaries than the matrix. The matrix was quite stable during secondary recrystallization with the aid of dense inhibitors. Finally, a complete secondary recrystallization microstructure consisting of large Goss grains was produced. The grain boundary characteristics distribution indicated that the high energy model was responsible for the abnormal growth of Goss grains under the present conditions. [ABSTRACT FROM AUTHOR]