| 摘要 |
The present invention provides an advantageous method for producing a high strength electrical steel sheet stably having high strength and high fatigue properties, and excellent magnetic properties, which is suitable for use as rotor material for high speed motors. The method includes: heating a slab having a predetermined chemical composition; then subjecting the slab to hot rolling consisting of rough rolling and finish rolling to obtain a hot rolled steel sheet; subjecting the steel sheet to subsequent hot band annealing and pickling; then subjecting the steel sheet to a single cold rolling to have a final sheet thickness; then subjecting the steel sheet to final annealing to produce a high strength electrical steel sheet, in which a cumulative rolling reduction ratio in the rough rolling is 73.0 % or more, in which in the hot band annealing step, an annealing condition is selected that satisfies an area ratio of recrystallized grains in a cross section in a rolling direction of the steel sheet after hot band annealing of 100 %, and a recrystallized grain size of 80 µm or more and 300 µm or less, under a condition where annealing temperature is 850 °C or higher and 1000 °C or lower, and annealing duration is 10 seconds or longer and 10 minutes or shorter, and in which in the final annealing step, an annealing condition is selected that satisfies an area ratio of recrystallized grains in a cross section in the rolling direction of the steel sheet after the final annealing of 30 % or more and 95 % or less, and a length in the rolling direction of a connected non-recrystallized grain group of 2.5 mm or less, under a condition where annealing temperature is 670 °C or higher and 800 °C or lower, and annealing duration is 2 seconds or longer and 1 minute or shorter. |
