PURPOSE: To produce a nonoriented silicon steel sheet excellent in magnetic properties in the circumferential direction with high productivity by subjecting a steel strip constituted of C, Si, Al, Mn, P, S, N, B and Fe to specified final finish annealing.
CONSTITUTION: A steel contg., by weight, ≤0.005% C, ≤2% Si, ≤1% Al so as to satisfy ≤0.2% Si+Al, ≤0.5% Mn, ≤0.2% P, ≤0.03% S, ≤0.004% N, ≤0.0005% B, and the balance Fe with inevitable impurities is subjected to cold rolling to regulate its sheet thickness to a final product one. The obtd. strip is subjected to final finish annealing in such a manner that it is heated preferably at about ≥20°C/sec heating rate to transform the α phase into the two phases of α+γ. After that, the strip is immediately cooled preferably at about ≥1°C/sec cooling rate without executing soaking to transform the two phases of α+γ into the α phase. After that, the strip is preferably coated with an insulated film or an adhesive film.
SHIMAZU TAKAHIDE
KOSUGE KENJI
SADAMASA TAKASHI
