To form a uniform, good-quality and high tensile strength glass film and to provide a steel sheet having excellent magnetic properties by using a separation agent at annealing, prepared by mixing MgO and a specific amount of a specific solid solution type combined hydroxide, at the final finish annealing for a grain oriented silicon steel sheet.
A separation agent at annealing, in which a solid solution type combined hydroxide represented by the general formula M21-xM3x(OH)2+x-nyyAn-.mH2O is mixed at a rate of 0.5-15 pts.wt. based on 100 pts.wt. of MgO, is used. In the formula, M2+ is one or more divalent metals selected from Be, Mg, Ca, Ba, Sr, Sn, Mn, Fe, Co, Ni, Cu, and Zn, M3+ is one or more elements selected from Al, Fe, Cr, Co, In, B, Ga, and Ti, An- is an n-valent anion, such as OH-, F-, Cl-, Br-, CO32-, SO42-, SiO32-, HPO42-, CH3COO-, Fe(CN)63- and HBO32-, (x) and (y) stand for 01-and 0-2, respectively, and (m) is the number of molecules of interlamellar water.
YAMAZAKI KOJI
KITAGAWA HISAKAZU
TANAKA OSAMU
NITTETSU PLANT DESIGNING CORP