Method for manufacturing grain-oriented electrical steel sheet

A method for manufacturing a grain-oriented electrical steel sheet, the method comprising:

• a hot rolling step of heating and hot rolling a slab including, as a chemical composition, by mass %,
• C:
• 0.020% to 0.150%,
• Si:
• 3.00% to 4.00%,
• Mn:
• 0.01% to 0.50%,
• S:
• 0.0010% to 0.0400%,
• acid-soluble Al:
• 0.010% to 0.050%,
• N:
• 0.002% to 0.020%,
• Bi:
• 0.0000% to 0.0200%,
• P:
• 0.000% to 0.100%,
• Sn:
• 0.00% to 0.50%,
• Cu:
• 0.00% to 0.50%,
• Cr:
• 0.00% to 0.50%,
• Sb:
• 0.00% to 0.20%,
• Mo:
• 0.00% to 0.10%,
• Nb:
• 0.0000% to 0.0200%,
• B:
• 0.0000% to 0.0200%,
• Te:
• 0.0000% to 0.0200%,
• Ni:
• 0.00% to 0.20%,
• Se:
• 0.0000% to 0.0200%, and
• a balance comprising Fe and impurities to obtain a hot-rolled steel sheet;
• a hot-rolled sheet annealing step of subjecting the hot-rolled steel sheet to hot-rolled sheet annealing to obtain a hot-band annealed sheet and then immersing the hot-band annealed sheet in a pickling solution;
• a cold rolling step of subjecting the hot-band annealed sheet to cold rolling to obtain a cold-rolled steel sheet;
• a decarburization annealing step of subjecting the cold-rolled steel sheet to decarburization annealing to obtain a decarburization-annealed sheet;
• a separator applying step of applying an annealing separator containing MgO, Al2O3, and a chloride to a surface of the decarburization-annealed sheet;
• a finish annealing step of subjecting the decarburization-annealed sheet coated with the annealing separator to finish annealing to obtain a finish-annealed sheet;
• a surface treatment step of pickling a surface of the finish-annealed sheet to obtain a surface-treated steel sheet;
• and
• a tension-applying insulating coating forming step including an insulating coating chemical solution applying step of applying an insulating coating forming solution containing 80 mass % or more in total of aluminum phosphate and silica to a surface of the surface-treated steel sheet, and a baking step of subjecting the surface-treated steel sheet coated with the insulating coating forming solution to a heat treatment to form a tension-applying insulating coating on the surface of the surface-treated steel sheet, wherein
• the heat treatment in the baking step includes a temperature rising process and a soaking process,
• in the temperature rising process, an average temperature rising rate of the steel sheet in a steel sheet temperature range of 100° C. to 600° C. is 10° C./s to 400° C./s in an atmosphere having an oxygen concentration of 1 vol % to 21 vol % and a dew point of 0° C. to 30° C., and
• in the soaking process, a holding time, at a constant steel sheet temperature in a range of 800° C. to 1000° C. and in a soaking atmosphere whose hydrogen concentration is 1 vol % to 15 vol % and whose atmosphere dew point is a constant value in a range of −20° C. to +40° C., is 5 seconds to 200 seconds.