| 摘要 |
PROBLEM TO BE SOLVED: To sterilize a second order recrystallization and to make the magnetic flux very high in density by using a magnesia as the lower layer film of an annealing separating agent in the case of the secondary finishing recrystallization annealing of a Bi added grain-oriented silicon steel subjected to cold rolling cender high draft and consisting of AlN as a main inhibitor. SOLUTION: A steel containing, by weight, 0.02 to 0.1%C, 2.0 to 4.0 Si, 0.012 to 0.050 acid-soluble Al, 0.0030 to 0.0150% N, 0.0005 to 0.03% Bi, the balance Fe with inevitable impurities is hot-rolled, then subjected to cold rolling and second order recrystallization finish rolling by the conventional method to obtain the magnetic steel plate is made. In this time, the steel sheet surface after decarburizing annealing or nitriding annealing is coated with a water slurry consisting essentially of magnesia. Then, the powdery annealing separating agent is applied on the surface of the coating film of 0.5 to 3g/m<2> obtained by drying the applied water slurry by an electrostatic powder coating to form the upper layer coating film of 3 to 20g/m<2> , thereafter the steel sheet is wound up and subjected to the secondary recrystallization annealing. |
