Microstructure, texture evolution and magnetic properties of strip-casting non-oriented 6.5 wt.% Si electrical steel sheets with different thickness

Abstract

0.15, 0.2, 0.3 and 0.5mm 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 //ND (λ-fiber) texture. After hot rolling, the intensity of the //ND texture was a little weakened and the microstructure was inhomogeneous. The warm rolling microstructures could be divided in two types, one characterized by in-grain shear bands (0.5mm thick sheet) and the other constituted of newly recrystallized grains (0.15∼0.3mm thick sheets), due to the difference in the warm rolling and interpass thermal treatment temperatures. The warm rolling texture was dominated by the mixture of //RD (γ-fiber) texture and //ND (γ-fiber) texture which was intensified in the 0.15∼0.3mm thick sheets. After annealing, //ND and parallel α-fiber textures were formed in the 0.5mm thick sheet, while //ND texture was nearly absent, but the 0.15∼0.3mm thick sheets were still dominated by //ND texture. The magnetic induction of the annealed sheet was much superior to that of the CVD product.