| 摘要 |
An oriented magnetic steel sheet with a very low core loss and a process for manufacturing it at a lower cost are disclosed. The steel sheet consists essentially of Si: greater than 3.0% and at most 6.0%, Mn: greater than 2.0% and at moat 8.0%, sol. Al: 0.003-0.015%, with Si (%)-0.5xMn (%)</=2.0 and the balance being Fe and incidental impurities, The amounts of C, N, and S as impurities are respectively at most 0.005%, at most 0.006%, and at most 0.01%. This steel sheet can be produced from a slab containing up to 0.01% C., up to 0.01% S and 0.001-0.010% N by (i) hot rolling the slab to obtain a hot-rolled steel sheet, (ii) cold rolling the hot-rolled steel sheet, as hot-rolled or after being subsequently annealed, one or more times with an intermediate annealing performed between successive stages of cold rolling to prepare a cold-rolled sheet, (iii) causing primary recrystallization by continuous annealing of the cold-rolled sheet, and (iv) finish annealing the continuously annealed steel sheet. The cold rolling may be carried out at a sheet temperature of 70 DEG -300 DEG C. The finish annealing preferably comprises causing secondary recrystallization by holding the annealed sheet in a temperature range of 825 DEG -925 DEG C. for 7-100 hours in a nitrogen-containing atmosphere, and holding the secondary-recrystallized sheet in a temperature range greater than 925 DEG C. and up to 1050 DEG C. for 4-100 hours in a hydrogen atmosphere to carry out purification annealing.
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