| 摘要 |
PURPOSE: To produce a silicon steel sheet excellent in magnetic properties and blankability by peeling a film by thermal stress generated at the time of temp. lowering in the latter stage of finish annealing. CONSTITUTION: For example, a steel stock contg., by weight, 0.01 to 0.10% C, 2 to 4.5% Si, 0.03 to 0.10% Mn or the like is subjected to hot rolling and cold rolling to finish its sheet thickness into a final one, and decarburizing annealing is executed in wet hydrogen to form an oxidized layer on the surface of the steel sheet. After that, it is applied with a separation agent for annealing having a compsn. consisting of 10 to 20% MgO, 20 to 50% Al2 O3 , and the balance SiO2 , and finish annealing is executed. Thus, a ceramic film in which the coefficient of linear expansion is regulated to <=0.5 times that of a silicon- contg. material is formed in the process of the finish annealing, and the film is peeled by thermal stress generated between the film and the stock at the time of temp. lowering after the subsequent finish annealing. In this way, the precipitation of nitrides in the vicinity of the surface layer of ferrite can be suppressed by the film formed in the process of the finish annealing. |
