PURPOSE: To obtain a low-grade electrical steel plate which is easy to grow crystal grains in stress relief annealing and has an excellent blanking property by regulating C, Si, Mn, P, S, Al and passing through the plate at specific temp. and tensile force after hot and cold rolling.
CONSTITUTION: After the steel of ≤0.10% C, ≤0.3% Si, <0.30% Mn, <0.08% P, ≤0.05% S, ≤0.005% Al is hot rolled, the steel plate heated at temp. above 400°C and below temp. of recrystallization in a continuous annealing furnace and is subjected to recovery annealing under ≥0.35kg/mm2 tension. Here, Mn, and P can be economized because the hardness of steel is regulated mainly by the recovery annealing. If Al more than the limits is in corporated, it hampers the growth of crystal grains in stress relief annealing. The temp. for the recovery annealing below the lower limit has no recovery effect, makes softening of the steel strip insufficient and does not contribute to the improvement in its flatness. In excess of the upper limit, the hardness of the steel strip decreases considerably from optimum blaking hardness. If the tension during the annealing is lower than the lower limit, the function of improving the flatness of the steel strip is low.
MATSUDA MASAYUKI
OKABE HISANARI
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