MAGNETIC STEEL PLATE WITH HIGH PERMEABILITY AND METHOD FOR MAKING SAME

A process for the production of oriented-grain high magnetic permeability steel sheet including the steps of continuously casting a steel slab haing a weight % composition within the range of 2.5-3.5 Si, 0.01-0.04 S, less than 0.07 C, less than 0.15 Mn, and an acid-soluble aluminum in an amount between 0.01 and 0.05, at a feed rate ranging from 700 to 1000 kg/minute, into an ingot mold of a length over 1200 mm and cooling it in said ingot mold with a quantity of water ranging from 2.8 to 4 m3 per ton of steel; heating the slab so obtained to 1300 DEG -1400 DEG C and immediately thereafter hot-rolling it to a thickness in the range between 2 and 3.1 mm, annealing the strip so obtained at a temperature in the range between 1050 DEG and 1150 DEG C, keeping it at this temperature for a duration between 5 and 30 seconds; cooling it at any desired cooling rate to 750 DEG -850 DEG C at a temperature at which austenite is still present in it; keeping the strip at this temperature for a duration ranging from 30 to 200 seconds; and finally quenching it from the initial quenching temperature of 400 DEG C at a cooling rate of between 10 DEG C/second and 100 DEG C/second; cold-rolling the strip so obtained with a reduction rate ranging from 80 to 90% and subjecting it finally to the decarburization and recrystallization annealing operations as well as to other final anneals.