Patent ID: 8778095
Filing Date: 2014-07-15
Classification: B21B,C21D,C22C,C23C,H01F

Abstract:
1. A method of manufacturing a grain-oriented electrical steel sheet comprising: heating a silicon steel slab at 1280° C. or below, the silicon steel slab containing, in % by mass, Si: 0.8% to 7%, and acid-soluble Al: 0.01% to 0.065%, with a C content of 0.085% or less, a N content of 0.012% or less, a Mn content of 1% or less, and a S equivalent Seq., defined by “Seq.=[S]+0.406×[Se]” where [S] being S content (%) and [Se] being Se content (%), of 0.015% or less, a Cu content of 0.4% or less, and the balance of Fe and unavoidable impurities; hot rolling the heated silicon steel slab so as to obtain a hot-rolled steel strip; annealing the hot-rolled steel strip so as to obtain an annealed steel strip; cold rolling the annealed steel strip so as to obtain a cold-rolled steel strip; decarburization annealing the cold-rolled steel strip so as to obtain a decarburization-annealed steel strip wherein primary recrystallization occurs during the decarburization annealing; coating an annealing separating agent on the decarburization-annealed steel strip; and finish annealing the decarburization-annealed steel strip so as to cause secondary recrystallization, wherein the method further comprises performing a nitriding treatment in which a N content of the decarburization-annealed steel strip is increased between start of the decarburization annealing and occurrence of the secondary recrystallization in the finish annealing, the hot rolling the heated silicon steel slab comprises: finish rolling with a finish temperature of 950° C. or below; and starting cooling within 2 seconds after completion of the finish rolling, and coiling at 700° C. or below, a heating rate of the hot-rolled steel strip within the temperature range from 800° C. to 1000° C. in the annealing the hot-rolled steel strip is 5° C./sec or above, and a cooling rate over a duration from the completion of the finish rolling up to a start of the coiling is 10° C./sec or above and 16° C./sec or below.