| 摘要 |
PURPOSE:To obtain an extremely low iron loss by combining three things; the reduction of the sheet thickness of a product, the formation of a forsterite film on the surface of a steel sheet to an adequate thickness and the reduction of the crystal grain size of the product. CONSTITUTION:A grain oriented silicon steel stock contg., by weight %, 2-4 Si, 0.01-0.035>=1 kinds of Se and S as an inhibitor, and 0.01-0.08>=1 kinds among Sb, As, Bi, and Sn is used. Such steel stock is subjected to hot rolling then to one pass or >=2 passes of cold rolling including intermediate annealing to a final sheet thickness of 0.15-0.25mm thickness. The steel sheet is then subjected to decarburization annealing and after a separating agent for annealing is coated thereon, the steel sheet is subjected to the final annealing to effect secondary recrystallization and to form the forsterite film at 1-4g/m<2> per face on the surface of the steel sheet. Then the heating rate to attain the decarburization annealing temp. after the final cold rolling is controlled to maintain the average crystal grain size after the secondary recrystallization to a 1-6mm range.
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