Dependence of recrystallization behavior on initial Goss orientation in ultra-thin grain-oriented silicon steels

Based on cold rolling and primary recrystallization method, 0.05-0.15 mm-thick ultra-thin grain-oriented silicon steel sheets were successfully produced by utilizing the high induction (Hi-B) and common grain-oriented (CGO) silicon steels as raw materials, respectively. Thus, the effects of sharpness of initial Goss texture on the evolutions of microstructure, texture and magnetic property were investigated in detail. For Hi-B steel, 'smooth' microstructures were formed in the cold-rolled sheets, and the textures evolved along the following path: exact {1 1 0} <0 0 1> -> {2 3 0}<0 0 1> -> {1 1 1}<1 1 2>. By contrast, significant deformation bands or shear bands were observed in the CGO steel, and the textures developed along the following path: deviated {1 1 0}<0 0 1> ->{2 1 0} <0 0 1> -> {1 1 1}<1 1 2>. After annealing, inhomogeneous microstructures containing some clusters with large grains (similar to 2-4 mm) and fine equiaxed grains appeared in the Hi-B steel and the associated texture evolution with increasing cold rolling reduction followed the path: {1 1 0}<0 0 1> -> {2 3 0}<0 01> -> {2 1 0}<0 0 1>. Unlike the Hi-B steel, relatively fine and uniform equiaxed recrystallization grains were produced in the final CGO steel, and the texture evolved along the route: {2 1 0}<0 0 1> -> {6 1 0}<0 01>. Consequently, further research focusing on the recrystallization mechanism was studied. The results showed that {1 1 0}<0 0 1> and {2 1 0}<0 0 1> developed into the predominated components due to oriented growth and oriented nucleation respectively in the 0.05 mm-thick Hi-B sheet, while {1 0 0}<0 0 1> became the main texture with the aid of oriented nucleation advantage in the CGO sheet. In addition, more attention was paid on the magnetic properties of the ultra-thin sheets, and the results showed that heavy cold rolling reduction as well as low annealing temperature contributed to better magnetic induction. Furthermore, the separated iron loss components were obtained to clarify the relationships between the iron loss and grain size, texture and thickness.