Patent ID: 8366836
Filing Date: 2013-02-05
Classification: C21D,C22C,C23C,H01F

Abstract:
1. A manufacturing method of a grain-oriented electrical steel sheet, comprising: at a predetermined temperature, heating a silicon steel material containing Si: 0.8 mass % to 7 mass %, acid-soluble Al: 0.01 mass % to 0.065 mass %, N: 0.004 mass % to 0.012 mass %, Mn: 0.05 mass % to 1 mass %, and B: 0.0005 mass % to 0.0080 mass %, the silicon steel material further containing at least one element selected from a group consisting of S and Se being 0.003 mass % to 0.015 mass % in total amount, a C content being 0.085 mass % or less, and a balance being composed of Fe and inevitable impurities; hot rolling the heated silicon steel material 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 one time or more 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 in which primary recrystallization is caused; coating an annealing separating agent containing MgO as its main component on the decarburization-annealed steel strip; and causing secondary recrystallization by finish annealing the coated decarburization-annealed steel strip, wherein the method further comprises performing a nitriding treatment in which an 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, wherein: in a case when S and Se are both contained in the silicon steel material, the predetermined temperature is lower than each of T in a case when S is contained but no Se is contained in the silicon steel material, the predetermined temperature is lower than each of T in a case when Se is contained but no S is contained in the silicon steel material, the predetermined temperature is lower than each of T a finish temperature Tf of finish rolling in the hot rolling satisfies inequation (4) below, and amounts of BN, MnS, and MnSe in the hot-rolled steel strip satisfy inequations (5), (6), and (7) below, wherein, [Mn] represents a Mn content (mass %) of the silicon steel material, [S] represents an S content (mass %) of the silicon steel material, [Se] represents a Se content (mass %) of the silicon steel material, [B] represents a B content (mass %) of the silicon steel material, [N] represents an N content (mass %) of the silicon steel material, B