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

摘要

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 percent Si-1 percent Mn-0.05 percent 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 SiO_2, which promoted decarburization. During the lamination annealing in a ferrite and austenite two phase region of about 1350K, the sheet materials were decarburized down to about 0.001 percent 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 percent of which were well aligned with the cube orientation. The doubly oriented steel sheets thus obtained showed a large magnetic induction of 1.87T at 800 A/m, a small core loss of 1.2W/kg at 1.5T and 60Hz and a low magnetostriction of 2.5 X 10~(-6) at 1.9T 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.