PURPOSE: To produce a grain-oriented silicon steel sheet excellent in magnetic properties and adhesive strength of film by regulating the furnace atmosphere in the course of temp. rise to a nonoxidizing atmosphere at the time of applying decarburizing annealing to a silicon-containing steel stock.
CONSTITUTION: A silicon-containing steel stock of about 3.28% Si content is hot-rolled, and the resulting plate is cold-rolled once or is cold-rolled twice or more while process- annealed between the cold rolling stages so as to be formed to the final sheet thickness. Subsequently, the resulting cold rolled steel sheet is subjected to decarburizing annealing and further to finish annealing. At this time, in the above decarburizing annealing, the furnace atmosphere in the course of temp. rise until a decarburizing soaking temp. of about 750-900°C is reached is regulated to nonoxidizing atmosphere. As the above atmosphere, a dry gas, such as Ar, He, N2, and H2, is used. In the course of soaking after temp. rise, the atmosphere is regulated to wet-gas atmosphere. By this method, the grain-oriented silicon steel sheet improved in iron loss and magnetic flux density and excellent in adhesive strength of film, external appearance, and space factor can be obtained.
ISHITOBI HIROTAKE
YAMAGUCHI KATSURO
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