UNIDIRECTIONAL MAGNETIC STEEL SHEET AND METHOD OF ITS MANUFACTURE

摘要

The present invention provides a grain-oriented electrical steel sheet having magnetic properties equal to, or higher than, those of conventional steel sheets can be produced economically with high productivity, and a method for producing such a steel sheet. The producing method comprises the steps of using, as a starting material, a coil obtained by heating a slab having a composition comprising, in terms of percent by weight, 0.02 to 0.15% of C, 2.5 to 4.0% of Si, 0.02 to 0.20% of Mn, 0.015 to 0.065% of Sol. Al, 0.0030 to 0.0150% of N, 0.005 to 0.040% as the sum of at least one of S and Se and the balance substantially consisting of Fe and hot rolling the slab to a coil, or a coil directly cast from a molten steel having the same components as the slab, conducting hot rolled sheet annealing at 900 to 1,100°C, one stage cold rolling the sheet by a tandem mill having a plurality of stands, conducting decarburization annealing, further conducting final finish annealing, and then applying final coating so that a product having a thickness of 0.20 to 0.55 mm, an average grain diameter size of 1.5 to 5.5 mm, a W 17/50 value expressed by the formula given below and a B 8 value satisfying the relation 1.80 ‰¦ B 8 (T) ‰¦ 1.88: 0.5884 e 1.9154 t ‰¦ W 17 / 50 €ƒ W / kg ‰¦ 0.7558 e 1.7278 t [t: sheet thickness.]