Patent ID: 7976645

Claim:
A method of production of grain-oriented electrical steel sheet comprising: heating silicon steel containing, in mass %, Si: 0.8 to 7%, C: up to 0.085%, acid-soluble Al: 0.01 to 0.065%, N: up to 0.075%, Mn: 0.02 to 0.20%, S equivalent=S+0.406×Se: 0.003 to 0.05% to a temperature ranging from the lowest of temperatures T 1 , T 2 , and T 3 to not more than 1350° C., wherein T1=10062/(2.72−log([Al]×[N]))−273; T2=14855/(6.82−log([Mn]×[S]))−273; and T3=10733/(4.08−log([Mn]×[Se]))−273; and wherein [Al] is the mass % of Al, [N] is the mass % of N, [Mn] is the mass % of Mn, [S], is the mass % of S, [Se] is the mass % of Se, and T 1 , T 2 , and T 3 are measured in ° C.; hot rolling the heated silicon steel, producing a hot-rolled steel sheet; recrystallizing the hot-rolled sheet by heating to a temperature of 1000° C. to 1150° C.; then annealing the hot-rolled steel sheet at a temperature of 850° C. to 1100° C. to control lamella spacing in a grain structure of the annealed hot-rolled steel to at least 20 μm; subjecting the annealed hot-rolled steel sheet to one cold rolling or a plurality of cold rollings with intermediate annealing to form a cold-rolled steel sheet of a final thickness, decarburization annealing the cold-rolled steel sheet, wherein, during the decarburization annealing, the cold-rolled steel sheet is heated in a temperature range of from 550° C. to 720° C. in a heating process consisting of only induction heating at a heating rate of at least 40° C./s; coating the decarburized steel sheet with an annealing separator, conducting finish annealing and a process to increase an amount of nitrogen in the steel sheet after decarburization annealing and before initiation of a secondary recrystallization in the finish annealing.