MANUFACTURE OF ELECTRICAL STEEL PLATE WITH LESS AGE HARDENING AT NORMAL TEMPERATURE

摘要

PURPOSE:To manufacture at a low cost an electrical steel plate which is excellent in magnetic characteristic, also is free from age hardening phenomenon at normal temperature, and has a stable punching characteristic, by executing a proper heat treatment to a steel band which has a limited composition of C, Si, P and acid-soluble Al. CONSTITUTION:A steel band consisting of 0.006-0.08% C, =1.5% Si, =0.2% P, =0.5% Al (acid-soluble Al), and the balance iron with inevitable impurities which is subjected to regular hot rolling and cold rolling, is recrystallized and annealed at 650-900 deg.C by a high-speed continuous annealing equipment, and then, quickly cooled to an overaging treatment temperature range or below at cooling speeds of 100-1,000 deg.C/sec, subsequently, an overaging treatment is executed for 60 seconds, or more within a temperature range of 300-500 deg.C, and the generation of an age hardening phenomenon is prevented by deposting a supersaturated solid solution C as coarse carbide. Also, when normalized rolling is executed under light pressure of 2-15% after the overaging treatment, a steel plate having excellent magnetic characteristics is obtained after stress relieving annealing.