Fine-Grained Doubly Oriented Silicon Steel Sheets and Mechanism of Cube Texture Development

Abstract

An attempt has been made to obtain strongly cube-textured sheet steels with fine grains employing oxide-separator-induced decarburization. The steels of the chemical compositions around Fe–3%Si–1%Mn–0.05%C were hot-rolled, twice cold-rolled with in-between annealing into 0.35 mm thickness and then subjected to the lamination annealing with separators containing SiO2, which promoted decarburization. During the lamination annealing in a ferrite and austenite two phase region of about 1350 K, the sheet materials were decarburized down to about 0.001% of carbon concentration. At the same time, the cube texture {100}〈001〉 remarkably evolved in the columnar ferrite grains which grew inward from sheet surfaces. Cube-oriented nuclei emerged during the primary recrystallization prior to decarburization, and they selectively grew in the columnar grains. After complete decarburization, the sheet materials consisted of ferrite grains of about 0.4 mm diameter, more than 90% of which were well aligned with the cube orientation. The doubly oriented steel sheets thus obtained showed a large magnetic induction of 1.87 T at 800 A/m, a small core loss of 1.2 W/kg at 1.5 T and 60 Hz and a low magnetostriction of 2.5×10−6 at 1.9 T in both the rolling and transverse directions. It is likely that the cube texture component arises from a near-{410}〈001〉 component present after intermediate annealing and preferentially grows by surface energy difference. The magnetization processes are also discussed.