| 摘要 |
PROBLEM TO BE SOLVED: To reduce core loss in a steel sheet by allowing it to have a specified compsn. contg. Si, Mn, Al, S, and the balance substantial Fe and regulating the content of nitride in a region at a specified distance from the surface of the steel sheet after finish annealing to a specified value or below. SOLUTION: This steel sheet contains, by weight, <=4.0% Si, 0.05 to 1.0% Mn, 0.1 to 1.0% Al and <=0.001% S. Then, the content of nitride in a region within 30 μm from the surface of the steel sheet after finish annealing is regulated to <=300 ppm. As for S as the contained element, in the case it is regulated to 0.001%, namely, to >=10 ppm, its remarkable core loss resistance can be attained, but, even if it is furthermore reduced, reduction in the core loss is made mild, and the core loss can not be regulated to <=2.4 W/kg. This is because a nitriding layer remarkably formed in the region of S<=10 ppm disturbs the growth of the crystal grains in the surface layer part to suppress reduction in the core loss. Therefore, the nitriding layer in the surface layer part of the steel sheet is removed by pickling after finish annealing. |
