Patent ID: 9175362
Filing Date: 2015-11-03
Classification: C21D,C22C,C23C,H01F

Abstract:
1. A method of manufacturing a grain-oriented electrical steel sheet, comprising: hot rolling a steel containing Si: 2.5 mass % to 4.0 mass %, C: 0.02 mass % to 0.10 mass %, Mn: 0.05 mass % to 0.20 mass %, acid-soluble Al: 0.020 mass % to 0.040 mass %, N: 0.002 mass % to 0.012 mass %, S: 0.001 mass % to 0.010 mass %, and P: 0.01 mass % to 0.08 mass %, further containing at least one selected from the group consisting of Ti: 0.0020 mass % to 0.010 mass % and Cu: 0.010 mass % to 0.50 mass %, and a balance composed of Fe and inevitable impurities, to obtain a hot-rolled steel sheet; annealing the hot-rolled steel sheet to obtain an annealed steel sheet; cold rolling the annealed steel sheet to obtain a cold-rolled steel sheet; decarburization annealing and nitridation annealing the cold-rolled steel sheet to obtain a decarburized nitrided steel sheet; and finish annealing the decarburized nitrided steel sheet, wherein the step of decarburization annealing and nitridation annealing comprises: heating the cold-rolled steel sheet in a decarburizing and nitriding atmosphere; performing first annealing at a first temperature within a range of 700° C. to 850° C. and with a holding time of at least 15 seconds to effectively diffuse the nitrogen entering a surface of the cold-rolled steel sheet into a central portion of the cold-rolled steel sheet; and then performing second annealing at a second temperature within a range of 860° C. to 950° C. and with a holding time of at least 15 seconds to adjust primary recrystallized grains to a sufficient size.