Non-oriented electrical steel sheet with low core-loss and high strength and method for manufacturin

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PURPOSE : A non-oriented electrical steel sheet with low core loss and high strength and a manufacturing method thereof are provided to decrease the variations between magnetic properties and strength properties by performing the final annealing in a temperature range ensuring small variations of yield strength, thereby stably obtaining the properties of low core-loss and high strength. CONSTITUTION : A manufacturing method of a non-oriented electrical steel sheet with low core loss and high strength comprises a step of hot-rolling and cold- rolling of a slab, and a step of final annealing the slab to obtain 1-50% of area fraction of an un-recrystallized structure at the cross section of a steel sheet. The slab consists of C of 0.005 wt.% or less, Si of 4.0 wt.% or less, P of 0.1 wt.% or less, S of 0.03 wt.% or less, Mn of 0.1-2.0 wt.%, Al of 0.3-2.0 wt.%, N of 0.003 wt.% or less, Ti of 0.005 wt.% or less, at least one from the group consisting of Ni : 5 wt. % or less and Cr : 10 wt. % or less, and Fe and inevitable impurities of the remaining amount. The final annealing is performed in a temperature range ensuring that the variations of yield strength are 3.0MPa or less. The average size of recrystallized grain after final annealing is controlled to be less than 10micrometers. The elongation ratio of the steel sheet by performing final annealing is controlled to be more than 20%, and the yield strength is controlled to be more than 500MPa.