PURPOSE: To eliminate the necessity for a magnetic annealing process after molding and obtain an internal magnetic shield provided with good mechanical strength and blackening film quality while fully holding a magnetic shielding effect, by fixing N as a compound of AlN to a cold rolled steel belt, in composition mainly composed with Fe and contained with C, Mn, SolAl, N and impurities, press molding the cold rolled steel belt and then applying surface blackening treatment.
CONSTITUTION: An ultra-low carbon steel belt, fixed as a compound of AlN by precipitation treatment, in composition mainly composed with Fe and contained with 0.01wt% C or less, 0.1W0.3wt% Mn, Al and N, where Al and N are 0.01W 0.06wt% and 0.02W0.1wt% respectively in a solid solution state, is press molded and then heated for 10W30min in a wet atmosphere at 550W600°C, thus surface blackening treatment is applied to obtain specific permeability at least 600 in crystal grain size ASTM8. A crystal grain is not formed large in the crystal grain size ASTM8, and a magnetic shield, with good press molding and a fine blackening film also with sufficient mechanical strength, can be obtained.
MORIYAMA GIICHI
ASHIZAKI SHIGEYA
TANAKA NOBUYUKI
