To form linear grooves of desired groove width on a metal strip surface and provide a grain-oriented electrical steel sheet having excellent magnetic properties, a linear groove formation method comprises: forming a resist coating on at least one surface of a metal strip; thereafter irradiating the resist coating with a laser while scanning the laser in a direction crossing a rolling direction of the metal strip, to remove the resist coating in a part irradiated with the laser; and thereafter performing etching treatment to form a linear groove in a part of the metal strip in which the resist coating is removed, wherein the resist coating contains a predetermined amount of an inorganic compound, and on the surface of the metal strip, the laser has a predetermined elliptic beam shape.

Provided is a steel component with excellent surface fatigue strength. The steel component has a nitride compound layer with a thickness of 5.0 μm to 30.0 μm and a hardened layer in an order from a component surface to a component inside, where a thickness of a porous layer on an outermost surface of the nitride compound layer is 3.0 μm or less and 40.0% or less of a thickness of the nitride compound layer, and the hardened layer has a hardness of HV600 or more at a position of 50 μm inward from the component surface, a hardness of HV400 or more at a position from the component surface to the component inside of 400 μm, and a hardness of HV250 or more at a position from the component surface to the component inside of 600 μm.

Provided is a grain-oriented electrical steel sheet which has been subjected to heat-resistant magnetic domain refining treatment and can effectively suppress carburizing and nitriding during stress relief annealing. The grain-oriented electrical steel sheet has a plurality of grooves on one side that extend linearly across the rolling direction and are lined up at intervals in the rolling direction, and has at least a forsterite film on a surface of the steel sheet, where an average thickness of the forsterite film formed on the floor of the grooves is 0.45 μm or more, and a standard deviation a of the thickness is 0.34 μm or less.

A grain-oriented electrical steel sheet according to the present invention has a steel sheet surface provided with grooves. An average protrusion height of the surface protrusion extending along a longitudinal direction of the groove is more than 5 μm and not more than 10 μm. When the surface protrusion is viewed in a cross section including the longitudinal direction of the groove and a normal direction of the steel sheet surface, the surface protrusion includes specific portions each having a height of 50% or more with respect to a height of each peak point appearing on a profile line of the surface protrusion. In the longitudinal direction of the groove, the total length of the specific portions is a length of 30% or more with respect to an overall length of the surface protrusion.

A high permeability grain oriented electrical steel having a chemistry comprising, all in weight percent, 2.5% to 4.5% silicon, 0.02% to 0.08% carbon, 0.01 to 0.05% aluminum, 0.005% to 0.050% sulfur or selenium, 0.02 to 0.20% manganese, 0.05 to 0.20% tin, 0.05 to 1% copper, 0.5% to 2.0% chromium, up to 0.10% phosphorus and up to 0.20% antimony with the balance being essentially iron and residual elements. The steel contains chromium and phosphorus in such amounts that a Cr:(P+0.25Sb) ratio is below 80:1 or, below 50:1, or below 30:1 which provides highly stable magnetic properties in the finished steel sheet. A hot processed band comprised of such steel is annealed and rapidly cooled after such annealing at a rate of at least 50° C. per second from 875-950° C. to a temperature below 400° C. prior to cold rolling to final thickness. Such steel forming a hot processed band having a thickness of from 1.5 to 4.0 mm and having a volume resistivity of at least 50 μΩ-cm, an austenite volume fraction (γ1150° C.) of at least 20%, and an isomorphic layer thickness of at least 2% of the total thickness on at least one surface of the hot processed band.

A motor comprising a steel sheet used as a core material of the motor, wherein the steel sheet includes a composition including: by mass %, 0.010% or less of C; 2.0% to 7.0% of Si; 2.0% or less of Al; 0.05% to 1.0% of Mn; 0.005% or less of S; 0.005% or less of N; and balance Fe and inevitable impurities; the steel sheet includes a magnetic flux density changing area where a change ΔB in magnetic flux density to a change ΔH=50 A/m in a magnetic field, is equal to or higher than 0.50 T; a thickness of the steel sheet is 0.05 mm to 0.20 mm; and an eddy-current loss of the steel sheet, at 1000 Hz−1.0 T, is equal to or less than 0.55 of a total iron loss.

A motor comprising a steel sheet used as a core material of the motor, wherein the steel sheet includes a composition including: by mass %, 0.010% or less of C; 2.0% to 7.0% of Si; 2.0% or less of Al; 0.05% to 1.0% of Mn; 0.005% or less of S; 0.005% or less of N; and balance Fe and inevitable impurities; the steel sheet includes a magnetic flux density changing area where a change ΔB in magnetic flux density to a change ΔH=50 A/m in a magnetic field, is equal to or higher than 0.50 T; a thickness of the steel sheet is 0.05 mm to 0.20 mm; and an eddy-current loss of the steel sheet, at 1000 Hz−1.0 T, is equal to or less than 0.55 of a total iron loss.

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.

Grain-oriented electrical steel sheet excellent in magnetic properties and adhesion of a primary coating to a base steel sheet and with few defects where the base metal is exposed in point defects and a method for manufacturing grain-oriented electrical steel sheet are provided. This is characterized by being provided with a base steel sheet and a primary coating. The primary coating satisfies (1) Number density D3 of Al concentrated regions: 0.015 to 0.150/μm.sup.2 (2) (Area S5 of regions comprised of anchoring oxide layer regions and Al concentrated regions)/(area S3 of Al concentrated regions)≥0.30, (3) Distance H5 of mean value of heights in thickness direction of regions of comprised of anchoring oxide layer regions and Al concentrated regions minus HO: 0.4 to 4.0 μm, (4) (Perimeter L5 of regions comprised of anchoring oxide layer regions and Al concentrated regions)/(observed area S0): 0.020 to 0.500 μm/μ.sup.2, and (5) (Area S1 of anchoring oxide layer regions)/(observed area S0)≥0.15.

A grain-oriented electrical steel sheet has a steel sheet and an insulating coating which is formed on a surface of the steel sheet. In the insulating coating, a metal phosphate and a colloidal silica are contained, the colloidal silica is contained in an amount of 20 to 150 parts by mass with respect to 100 parts by mass of the metal phosphate, one or more kinds of fine particles selected from the group consisting of silicon carbide, silicon nitride, aluminum nitride, boron nitride, sialon, and cordierite are further contained in an amount of 0.5 to 7 parts by mass with respect to 100 parts by mass of the metal phosphate, an average particle size of the fine particles is 0.3 to 7.0 μm, crystallized ratio of the metal phosphate is 2% to 40%, and chromium is not contained.