| 摘要 |
PROBLEM TO BE SOLVED: To increase the relative permeability in the DC magnetic field in a steel sheet, to make better the geomagnetic shield characteristics thereof and to improve its strength by subjecting a slab having a specified chemical compsn. to hot rolling, executing cold rolling and thereafter conducting anneaing type continuous hot-dip galvanizing. SOLUTION: The compsn. of a slab is composed of, by weight, 0.0008 to 0.0050% C, 0.3 to 1.8% Si, 0.5 to 1.8% Mn, <=0.12% P, 0.002 to 0.020% S, 0.020 to 0.060% Al, 0.01 to 0.06% Ti, <=0.0030% N, and the balance Fe. This slab is discharged from a heating furnace at <1150 deg.C and is subjected to hot rolling at 800 to 980 deg.C finishing temp. It is coiled at >=700 deg.C, is subjected to 60 to 90% cold rolling and is thereafter annealed at 750 deg.C to the Ac3 point in continuous hot-dip galvanizing equipment having continuous annealing equipment. In this way, the high strength steel sheet in which ferrite grain size is regulated to 10 to 30μm, relative permeability in the DC magnetic field of 0.3 oersted is regulated to >=500 and which is good in geomagnetic shield characteristics can be obtd.
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