Microstructure, Texture Evolution, and Magnetic Properties of Strip-Casting Nonoriented 6.5 wt.% Si Electrical Steel Sheets With Different Thickness

Abstract

The 0.15, 0.2, 0.3, and 0.5 mm-thick 6.5 wt.% Si electrical steel sheets were produced by twin-roll strip casting, hot rolling, warm rolling, and annealing. A detailed study of the microstructure and texture evolution at different processing stages was carried out by optical microscopy and X-ray diffraction. The initial as-cast strip showed strong columnar grains and pronounced $\langle 001\rangle$ //normal direction (ND) texture. The hot rolled sheet with an inhomogeneous microstructure demonstrated slightly weakened $\langle 001\rangle$ //ND texture. The morphology of the warm rolling microstructure could be classified into two types. One was characterized by large amounts of in-grain shear bands (0.5 mm-thick sheet), whereas the other was constituted of the mixture of newly recrystallized grains and severely deformed grains (0.15–0.3 mm-thick sheets). The warm rolling texture was dominated by $\langle 110\rangle$ //rolling direction and $\langle 111\rangle$ //ND textures. The intensities of the $\langle 111\rangle$ //ND textures were higher in the 0.15–0.3 mm-thick warm rolled sheets. After annealing, the 0.5 mm-thick sheet showed $\langle 001\rangle$ //ND, parallel $\alpha$ -fiber, and very weak $\langle 111\rangle$ //ND textures, whereas the 0.15–0.3 mm-thick sheets presented strong $\langle 111\rangle$ //ND texture. The magnetic inductions of the 0.3 and 0.5 mm-thick sheets were superior to those of the corresponding CVD products.