PURPOSE: To form good sub-scale with thin films and to improve electromagnetic characteristics by executing the cooling in decarburization annealing of a silicon steel sheet in a neutral atmosphere gas of a specific concn. in production of a grain oriented electrical steel sheet.
CONSTITUTION: A silicon steel slab is hot rolled and is subjected to one pass or ≥2 passes of cold rolling including intermediate annealing to a final sheet thickness. The steel sheet is then subjected to decarburization annealing and is cooled in the neutral atmosphere gas of ≥40%. A separating agent for annealing is then applied on the steel sheet and is subjected to final finish annealing. The concn. of H2 in the atmosphere gas in cooling is required to be regulated to <60%. The non-reacted separating agent is removed from the steel strip after the final finish annealing and thereafter, an insulation coating agent is applied thereon at need and the steel strip is subjected to annealing for flattening, by which the steel strip is finished into products.