| 摘要 |
PROBLEM TO BE SOLVED: To stably obtain a mirror-finished grain-oriented silicon steel sheet with high magnetic flux density on an industrial scale by effectively combining the attainment of ultrahigh magnetic flux density by means of conventional Bi addition with the reduction of iron loss by means of mirror finishing technique by application of alumina. SOLUTION: A molten steel, having a composition consisting of, by weight, 0.02-0.1% C, 2.0-4.8% Si, 0.012-0.050% acid soluble Al, 0.030-0.150% N, 0.0005-0.03% Bi, and the balance Fe, is cast, hot-rolled, and subjected to cold rolling including final heavy cold rolling at 65-95%, while process-annealed between cold rolling stages, to the final sheet thickness. After decarburizing annealing, the resultant sheet is nitrided and subjected to secondary recrystallization finish annealing, by which a grain-oriented silicon steel sheet is produced. At this time, decarburizing annealing is performed in the atmospheric gas of a degree of oxidation free from formation of Fe oxides, or, the oxides resultant from decarburizing annealing are removed by acid pickling, and then, alumina is applied as a separation agent at annealing, by which the steel sheet surface after finish annealing is formed into mirror-finished state. By this method, the mirror-finished grain-oriented silicon steel sheet, having a magnetic flux density as high as >=1.95T B8 , can be obtained. |
