Abstract: It is a technical subject to advantageously avoid the degradation of surface properties in a low iron loss grain oriented silicon steel sheet as a material for transformers, particularly if it is intended to thin the gauge to 0.1.about.0.25 mm. A low iron loss grain oriented silicon steel thin sheet can stably be produced without causing the degradation of performances through strain relief annealing by considering a chemical composition in steel, optimizing the rolling conditions, particularly cold rolling conditions, and further forming heterogeneous microareas onto the steel sheet surface.

Abstract: An extra-low iron loss grain oriented silicon steel sheet is produced by irradiating electron beam to an insulation coating formed on a grain oriented silicon steel sheet after finish annealing in a direction crossing the rolling direction of the sheet, whereby the magnetic properties are not degraded even if the steel sheet is subjected to a strain relief annealing. If necessary, an inert gas may be introduced into the vicinity of electron beam irradiated zone of the coating.

Abstract: An extra-low iron loss grain oriented silicon steel sheet is produced by irradiating electron beam to an insulation coating formed on a grain oriented silicon steel sheet after finish annealing in a direction crossing the rolling direction of the sheet, whereby the magnetic properties are not degraded even if the steel sheet is subjected to a strain relief annealing. If necessary, an inert gas may be introduced into the vicinity of electron beam irradiated zone of the coating.

Abstract: As to a method of producing grain oriented silicon steel sheets used in stacked lamination-core transformers, which realizes the improvement of magnetic properties, particularly extreme reduction of iron loss irrespectively of a high temperature heat treatment such as strain relief annealing and can attain the improvement of compressive stress dependence of magnetostriction and lamination factor, it is a main point that the steel sheet after the finish annealing is provided on its surface with a thin coat of at least one layer composed mainly of nitrides and carbides of Ti, Zr, Hf, V, Nb, Ta, Mn, Cr, Mo, W, Co, Ni, Al, B and Si and strongly adhered to the surface of the steel sheet through a mixed layer of base metal and thin coat.

Abstract: This invention realizes the improvement of the surface properties and the magnetic characteristics in such a way that a large amount of Si of 3.1-4.5% is incorporated into a raw material, a small amount of Al and a very small amount of S or Se are used as inhibitor together with Mo, and the slab heating is so performed at a temperature of not lower than 1,270.degree. C. that the scale loss may reach 2.7-5.0%, whereby the inhibitor is fully dissociated and solid-solved to conspicuously strengthen the growth inhibiting effect against the primary recrystallization grains in the secondary recrystallization annealing for promoting the growth of the secondary recrystallization grains in the {110}<001> orientation, thereby forming the secondary recrystallization texture extremely strongly arranged in the {110}<001> orientation, so that a high magnetic flux density and a low iron loss is attained with effectively preventing cracks in hot rolling after slab soaking.