| 摘要 |
PURPOSE:To industrially provide the steel sheet free from glass film and having superior workability by specifying Si content and the amount of internal oxidation layer within the range between the position at a specific depth from the metallic surface of the steel sheet and the surface, respectively. CONSTITUTION:This steel sheet is an ultra-low iron loss grain-oriented silicon steel sheet which has a composition containing 1.0-7.0wt.% Si and where the amount of internal oxidation layer distributing within the region between the position at a depth of <=15mu from the metallic surface of the steel sheet and the surface is regulated to <=1% expressed in terms of oxygen content in the above thickness region. Further, this steel sheet is extremely increased in magnetic flux density and satisfies B8>=1.93T. The primary recrystallized grains in the steel sheet after annealing are regulated, by means of primary recrystallization annealing, so that those having a grain size more than twice the average grain size comprise <10%, in order to produce this steel sheet. Then a separation agent at annealing having a composition where 2-30 pts.wt. of the chlorides, carbonates, etc., of Li, K, Na, etc., are added to 100 pts.wt. of MgO is applied to the steel sheet. After finish annealing is applied to the steel sheet while regulating temp. rise rate in the range between 950 and 1150 deg.C to <=10 deg.C/hr and also regulating the atmosphere so that it consists of N2 and H2 and contains >=30% N2, heat flattening 15 done and, before and after this heat flattening, linear or dotlike flaws are provided to the surface of the steel sheet in a direction at 45 to 90 deg. with respect to the rolling direction. |
