Manufacturing method of cold rolled steel sheet with superior magnetic shield properties for mask-frame in braun-tube

摘要

PURPOSE: A method for manufacturing cold rolled steel plate for a CRT frame is provided to produce a frame material having superior magnetism shielding property of low coercive force and high magnetic permeability with grain size ASTM No. 7 or less by controlling conditions of cold rolling and skin pass reduction ratio of aluminum killed steel. CONSTITUTION: The method comprises the steps of homogenization treating an aluminum killed steel consisting of 0.005 wt.% of C, 0.02 wt.% or less of Si, 0.02 wt.% or less of Al, 0.02 to 0.06 wt.% of Cr, and a balance of Fe and other inevitable impurities, finally hot rolling the homogenization treated steel at a temperature of 870 deg.C or more, cold rolling the hot rolled steel to a final thickness with a reduction ratio of 40 to 60, continuous annealing the cold rolled steel, and skin passing the continuous annealed steel to a reduction ratio of 0.5 or less. The skin passed cold rolled steel has a 1.3 Oe or less of coercive force and 3500 or more of magnetic permeability with a grain size ASTM No. 7 or less.