A grain-oriented electrical steel sheet includes: a base steel sheet including, as a chemical composition, by mass %, C: 0.010% or less, Si: 2.50% to 4.00%, Mn: 0.050% to 1.000%, S+Se: 0.005% or less in total, Sol. Al: 0.005% or less, N: 0.005% or less, Bi+Te+Pb: 0% to 0.0300% in total, Sb: 0% to 0.50%, Sn: 0% to 0.50%, Cr: 0% to 0.50%, Cu: 0% to 1.0%, and a remainder of Fe and impurities; and a tension-applying insulation coating provided on a surface of the base steel sheet, in which, on the surface of the base steel sheet, an arithmetic average roughness Ra along a rolling 90° direction that is a direction perpendicular to a rolling direction is 0.60 μm or less, and when a cross section of the base steel sheet is observed along the rolling 90° direction, recessed parts having a depth of 0.1 μm or more and 2.0 μm or less are present on the surface of the base steel sheet in 1.0/100 μm or more and 6.0/100 μm or less.

A method for manufacturing a grain-oriented electrical steel sheet including a step of hot-rolling a slab containing a predetermined component composition with a remainder including Fe and an impurity to obtain a hot-rolled steel sheet, a step of, after carrying out hot-rolled steel sheet annealing on the hot-rolled steel sheet, carrying out cold rolling to obtain a cold-rolled steel sheet, a step of carrying out primary recrystallization annealing including a rapid temperature increase at an average temperature increase velocity V of 400° C./s or more and imparting of a steel sheet tensile force S on the cold-rolled steel sheet, and a step of applying an annealing separating agent to a surface of the cold-rolled steel sheet after the primary recrystallization annealing and then carrying out flattening annealing.

Disclosed is a grain-oriented electrical steel sheet including: closure domains, each containing a discontinuous region at a part thereof and extending at an angle within 30° with respect to a transverse direction of the steel sheet, wherein a closure domain overlapping portion in the discontinuous region on one surface of the steel sheet has a length α in the transverse direction that is longer than a length β in the transverse direction of the closure domain overlapping portion on the other surface of the steel sheet, and the length α satisfies 0.5≤α≤5.0 and the length β satisfies 0.2α≤β≤0.8α. Consequently, the iron loss and the deterioration of magnetostrictive properties are suppressed in discontinuous regions, which would be inevitably formed when magnetic domain refining treatment is performed using a plurality of irradiation devices.

Embodiments of the present invention comprise; annealing steel sheets (e.g., hot rolled steel sheets or thin cast strip steel); cold rolling the sheets in one or more cold rolling steps (e.g., with annealing steps between multiple cold rolling steps); and performing one or more of tension leveling, a rough rolling, or a coating process on the sheets after cold rolling, without an intermediate annealing step between the final cold rolling step and the tension leveling, the rough rolling, or the coating process, or the customer stamping or final customer annealing. In order to achieve the desired properties for the steel sheet, stamping and final annealing is performed by the customer. The new process provides an electrical steel with the similar, same, or better magnetic properties than an electrical steel manufactured using the traditional processing that utilizes an intermediate annealing step after cold rolling and before the stamping and final annealing.

A method for manufacturing an oriented electrical steel sheet according to an exemplary embodiment of the present invention includes: providing a slab including, as wt %, Si at equal to or less than 4.0% (excluding 0%), C at 0.001% to 0.4%, and Mn at 0.001% to 2.0%, and including a balance including Fe and inevitably mixed and input impurities; reheating the slab; manufacturing a hot steel sheet by hot-rolling the slab; performing hot-rolled steel sheet annealing to the hot steel sheet; primarily cold-rolling the hot-rolled steel sheet annealed hot steel sheet; decarburization-annealing the cold-rolled steel sheet; secondarily cold-rolling the decarburization-annealed steel sheet;

and finally annealing the cold-rolled steel sheet, wherein, regarding the finally annealed steel sheet, a size 2L of a magnetic domain existing in a grain is less than a thickness D of the steel sheet (2L<D).

In a grain-oriented electrical steel sheet which is manufactured from a thin slab without using an inhibitor forming component, excellent magnetic properties are stably achieved. In a method for manufacturing a grain-oriented electrical steel sheet, a slab heating and annealing are performed under specific conditions.

A method for producing a grain oriented electrical steel sheet includes a decarburization annealing process where an oxidation degree PH.sub.2O/PH.sub.2 is controlled, an annealing separator applying process where a mass ratio of MgO and Al.sub.2O.sub.3 in an annealing separator is controlled, a final annealing process where hydrogen in mixed gas atmosphere is controlled to 50 volume % or more, an annealing separator removing process where water-washing is conducted using solution with inhibitor and then pickling is conducted, a smoothing process where mixed gas and temperature are controlled for annealing, and an insulation coating forming process where a baking temperature and a heat treatment temperature are controlled.

The grain-oriented electrical steel sheet is a grain-oriented electrical steel sheet which does not have an inorganic coating containing forsterite as a main component, including a base steel sheet having a predetermined chemical component, a silicon-containing oxide layer provided on the base steel sheet, an iron-based oxide layer provided on the silicon-containing oxide layer, and a tension-insulation coating provided on the iron-based oxide layer, having a thickness of 1 to 3 μm, and containing phosphate and colloidal silica as main components. When elemental analysis is performed from a surface of the tension-insulation coating in a sheet thickness direction by glow discharge optical emission spectrometry, predetermined requirements are satisfied.

A method for manufacturing a grain-oriented electrical steel sheet includes: a silicon steel material production process of producing a silicon steel material; a hot rolling process of obtaining a hot rolled sheet by subjecting the silicon steel material to hot rolling; a cold rolling process of obtaining a steel sheet of a final sheet thickness by subjecting the hot rolled sheet to a single cold rolling process or multiple cold rolling processes having intermediate annealing performed between the cold rolling processes; a decarburization annealing process of subjecting the steel sheet to decarburization annealing; and a final annealing process of applying an annealing separator containing alumina as a main component to the steel sheet and subjecting the steel sheet to final annealing. The silicon steel material contains: in terms of mass %, Si: 0.8 to 7.0%; C: 0.085% or less; acid-soluble Al: 0.010 to 0.065%; N: 0.004 to 0.012%; Mn: 1.00% or less; S: 0.050% or less; a total of 0.01 to 0.20% of one or both of Sn and Sb; and the remainder: Fe and impurities.

A grain-oriented electrical steel sheet is a grain-oriented electrical steel sheet which does not have an inorganic coating containing forsterite as a main component and which includes: a base steel sheet containing a prescribed chemical component; a silicon-containing oxide layer provided on the base steel sheet; an iron-based oxide layer provided on the silicon-containing oxide layer; and a tension-insulation coating provided on the iron-based oxide layer, having a thickness of 1 to 3 μm, and containing phosphate and colloidal silica as main components. When the tension-insulation coating undergoes elemental analysis using a glow discharge optical emission spectrometry in a sheet thickness direction from a surface of the tension-insulation coating, a peak Si emission intensity satisfies a prescribed requirement.