A non-oriented electrical steel sheet according to one embodiment of the invention has a chemical composition represented by C: 0.0030% or less, Si: 2.00% or less, Al: 1.00% or less, Mn: 0.10% to 2.00%, S: 0.0030% or less, one or more selected from the group consisting of Mg, Ca, Sr, Ba, Nd, Pr, La, Ce, Zn, and Cd: 0.0003% or greater and less than 0.0015% in total, a parameter Q represented by Q=[Si]+2×[Al]−[Mn]: 2.00 or less; Sn: 0.00% to 0.40%, Cu: 0.00% to 1.00%, and a remainder: Fe and impurities, and a parameter R represented by R−(I.sub.100+I.sub.310+I.sub.411+I.sub.521)/(I.sub.111+I.sub.211+I.sub.332+I.sub.221) is 0.80 or greater.

A non-oriented electrical steel sheet according to an embodiment of the present invention includes, in wt%, Si: 2.2 to 4.5 %, Mn: 0.5 % or less (excluding 0 %), AI: 0.001 to 0.5 %, Sn: 0.07 to 0.25 %, and N: 0.0010 to 0.0090 %, and the balance of Fe and inevitable impurities.

A surface layer portion existing in an inner direction from a surface of the steel sheet and a central portion existing inside the surface layer portion are included, and the central portion includes N at 0.005 wt% or less, and the surface layer portion further includes N at 0.001 wt% or more compared to the central portion; and the surface layer portion has an average grain size of 60 .Math.m or less, while the central portion has an average grain size of 70 to 300 .Math.m.

A method for producing an austempered steel is provided. The method includes subjecting a steel alloy having a silicon content of 1.5 to 4.4 weight percent and a carbon content of 0.3 to 0.8 weight percent to continuous cooling followed by annealing. The cooling rate is initially sufficiently fast to prevent predominant formation of proeutectoid ferrite or pearlite, while subsequently at intermediate temperatures, the cooling rate is sufficiently slow to allow a transformation of the austenite to mainly ausferrite during cooling. The annealing is able to complete the transformation of carbon enriched austenite to ausferrite and to temper any martensite previously formed. The method results in the cost-efficient production of one or more continuously cooled and annealed austempered steel components or semi-finished products having mainly an ausferritic microstructure.

Provided is a grain-oriented electrical steel sheet that has excellent magnetic properties and can be manufactured by secondary recrystallization orientation control using coil annealing with high productivity. A grain-oriented electrical steel sheet comprises a specific chemical composition, wherein an average value of a deviation angle (α.sup.2+β.sup.2).sup.1/2 calculated from a deviation angle α from ideal Goss orientation around an ND rotation axis and a deviation angle β from ideal Goss orientation around a TD rotation axis is 5.0° or less, and an area ratio R.sub.β of crystal grains with β≤0.50° is 20% or less.

A grain-oriented electrical steel sheet includes: a base steel sheet having a predetermined chemical composition; a glass coating provided on the surface of the base steel sheet; and a tension-applying insulation coating provided on the surface of the glass coating, in which linear thermal strains having, a predetermined angle (φ) with respect to a transverse direction which is a direction orthogonal to a rolling direction are periodically formed on the surface of the tension-applying insulation coating at predetermined intervals along the rolling direction, a full width at half maximum F1 on the linear thermal strain and a full width at half maximum F2 at an intermediate position between the two linear thermal strains adjacent to each other satisfy 0.00<(F1−F2)/F2≤0.15, the width of the linear thermal strain is 10 μm or more and 300 μm or less, and in the base steel sheet, an orientation distribution angle γ around a rolling direction axis of secondary recrystallization grains, an orientation distribution angle α around an axis parallel to a normal direction, and an orientation distribution angle β around an axis perpendicular to each of the RD axis and the ND axis in units of ° satisfy 1.0≤γ≤8.0 and 0.0≤(α.sup.2+β.sup.2).sup.0.5≤10.0.

A grain-oriented electrical steel sheet includes: a base steel sheet having a predetermined chemical composition; a glass coating provided on the surface of the base steel sheet; and a tension-applying insulation coating provided on the surface of the glass coating, in which linear thermal strains having, a predetermined angle (φ) with respect to a transverse direction which is a direction orthogonal to a rolling direction are periodically formed on the surface of the tension-applying insulation coating at predetermined intervals along the rolling direction, a full width at half maximum F1 on the linear thermal strain and a full width at half maximum F2 at an intermediate position between the two linear thermal strains adjacent to each other satisfy 0.00<(F1−F2)/F2≤0.15, the width of the linear thermal strain is 10 μm or more and 300 μm or less, and in the base steel sheet, an orientation distribution angle γ around a rolling direction axis of secondary recrystallization grains, an orientation distribution angle α around an axis parallel to a normal direction, and an orientation distribution angle β around an axis perpendicular to each of the RD axis and the ND axis in units of ° satisfy 1.0≤γ≤8.0 and 0.0≤(α.sup.2+β.sup.2).sup.0.5≤10.0.

A non-oriented electrical steel sheet according to an embodiment of the present invention includes, in wt %, Si: 1.5 to 4.0%, Al: 0.1 to 1.5%, Mn: 0.05 to 1.5%, Sn: 0.015 to 0.1%, P: 0.005 to 0.05%, Ga: 0.001 to 0.004%, and Bi: 0.0005 to 0.003%, and the balance of Fe and inevitable impurities. An area fraction of texture in a {118}//ND orientation is higher than that of texture in a {111}///ND orientation.

A hot-rolled steel sheet for non-oriented electrical steel sheets includes, by mass %: C: 0.0010% to 0.0050%; Si: 1.90% to 3.50%; Al: 0.10% to 3.00%; Mn: 0.05% to 2.00%; P: 0.100% or less; S: 0.005% or less; N: 0.0040% or less; B: 0.0060% or less; Sn: 0% to 0.50%; Sb: 0% to 0.50%; Cu: 0% to 0.50%; REM: 0% to 0.0400%; Ca: 0% to 0.0400%; Mg: 0% to 0.0400%; and a remainder including Fe and impurities, in which a hardness H.sub.D of a deformed structure of a thickness middle portion (½t position) in a sheet width direction end portion of the hot-rolled steel sheet for non-oriented electrical steel sheets is Hv 220 or less.

A grain-oriented electrical steel sheet according to the present invention includes a base steel sheet having plural grooves on a surface and a glass film formed on the surface of the base steel sheet. In case of viewing region including grooves in cross section orthogonal to groove longitudinal direction, a straight line passing through peak point present on profile line of glass film and parallel to groove width direction orthogonal to sheet thickness direction in cross section is defined as reference line, a point present on boundary line between glass film and base steel sheet and present at lowest location in sheet thickness direction is defined as deepest point, and a point present on boundary line and present at the highest location in the sheet thickness direction in region having the deepest point in a center and having length of 2 μm in groove width direction is defined as shallowest point, a relationship between shortest distance A between reference line and deepest point and shortest distance B between reference line and shallowest point satisfies Expression (1).
0.1 μm≤A−B≤5.0 μm  (1)

A method for the recrystallisation annealing of a non-grain-oriented electric strip (2) in a continuous annealing and coating line (1) is presented. Therein, the electric strip (2) is heated in an induction furnace (5) to a temperature of at least 680° C. at a heating rate of at least 80 K/s and then, in an optional second continuous furnace (8), to a temperature of at least 820° C. at a heating rate of at most 20 K/s. The electric strip (2) is initially heated before the induction furnace (5) via a first continuous furnace (3) to a temperature of at least 300° C. at a heating rate of at most 60 K/s.