Silicon steel sheet and method for producing the same

A nonoriented silicon steel sheet having low iron loss at high frequency, the silicon steel sheet comprising:

• an upper surface layer, a lower surface layer and a steel sheet center portion;
• the silicon steel sheet having a Si concentration gradient in the sheet thickness direction so that the upper surface layer and the lower surface layer have a Si concentration higher than the Si concentration of the steel sheet center portion;
• the upper surface layer being at least 10% of the sheet thickness in the steel sheet thickness direction from the upper surface of the silicon steel sheet, and the lower surface layer being at least 10% of the sheet thickness in the steel sheet thickness direction from the lower surface of the silicon steel sheet;
• the upper surface layer and the lower surface layer having a Si concentration of 5 to 7.06 wt. %;
• the steel sheet center portion having a Si concentration of 3.57 wt. % to 4.79 wt. %;
• and
• the silicon steel sheet having a thickness of 0.2 mm or less.