In a laser processing apparatus for refining magnetic domains of a grain-oriented electromagnetic steel sheet by setting a laser beam to be focused on the grain-oriented electromagnetic steel sheet and scanned in a scanning direction, the laser beam focused on the grain-oriented electromagnetic steel sheet is linearly polarized light, and an angle between a linear polarization direction and the scanning direction is higher than 45° and equal to or lower than 90°.

In a laser processing apparatus for refining magnetic domains of a grain-oriented electromagnetic steel sheet by setting a laser beam to be focused on the grain-oriented electromagnetic steel sheet and scanned in a scanning direction, the laser beam focused on the grain-oriented electromagnetic steel sheet is linearly polarized light, and an angle between a linear polarization direction and the scanning direction is higher than 45° and equal to or lower than 90°.

Provided is a non-oriented electrical steel sheet having an average crystal grain size of crystal grains being not more than 80 μm, an area ratio of crystal grains having a grain size of not less than 1.5 times the average crystal grain size being not less than 10%; and an area ratio of crystal grains having aspect ratios of not more than 0.3 being not more than 20%, by subjecting a steel raw material containing, in mass %, C: not more than 0.005%, Si: 2.0 to 5.0%, Mn: 0.05 to 5.0%, Al: not more than 3.0%, and Zn: 0.0003 to 0.0050% to hot rolling, cold rolling, and cold-rolled sheet annealing and by heating the cold-rolled sheet to an annealing temperature between 700 to 850° C. at the average heating rate between 500 and 700° C. in a heating process of the cold-rolled sheet annealing to be not less than 10° C./s.

What is provided is a non-oriented electrical steel sheet having a chemical composition in which, by mass %, C: 0.010% or less, Si: 1.50% to 4.00%, sol. Al: 0.0001% to 1.0%, S: 0.010% or less, N: 0.010% or less, one or a plurality of elements selected from the group consisting of Mn, Ni, Co, Pt, Pb, Cu and Au: 2.50% to 5.00% in total are contained and a remainder includes Fe and impurities, in which a sheet thickness is 0.50 mm or less, and, in an arbitrary cross section, when an area ratio of {100} crystal grains is indicated by Sac, an area ratio of {110} crystal grains is indicated by Sag, and an area ratio of the {100} crystal grains in a region of up to 20% from a side where a KAM value is high is indicated by Sbc, Sac>Sbc>Sag and 0.05>Sag are satisfied.

Provided is a method for manufacturing a grain-oriented electrical steel sheet. A steel slab having a specific chemical composition is heated and hot rolled. A hot-rolled steel sheet thus obtained is subjected to hot band annealing to obtain a cold-rolled steel sheet, which is then subjected to primary recrystallization annealing to obtain a primary recrystallized steel sheet. An annealing separator is applied to the primary recrystallized steel sheet, which is then coiled. The coil is subjected to secondary recrystallization annealing to obtain a grain-oriented electrical steel sheet having 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 of 4.5° or less, and an area ratio R.sub.β of crystal grains with β≤0.50° of 15% or less.

Provided is a method for manufacturing a grain-oriented electrical steel sheet. A steel slab having a specific chemical composition is heated and hot rolled. A hot-rolled steel sheet thus obtained is subjected to hot band annealing to obtain a cold-rolled steel sheet, which is then subjected to primary recrystallization annealing to obtain a primary recrystallized steel sheet. An annealing separator is applied to the primary recrystallized steel sheet, which is then coiled. The coil is subjected to secondary recrystallization annealing to obtain a grain-oriented electrical steel sheet having 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 of 4.5° or less, and an area ratio R.sub.β of crystal grains with β≤0.50° of 15% or less.

A non-oriented electrical steel sheet according to an exemplary embodiment of the present invention includes, by weight %, Si: 2.5 to 6.0%, Al: 0.2 to 3.5%, Mn: 0.2 to 4.5%, Cr: 0.01 to 0.2%, P: 0.005 to 0.08%, Mg: 0.0005 to 0.05%, and a remainder including Fe and inevitable impurities, while satisfying Equation 1 below, and formed with an inner oxidation layer of a 0.2 to 5 μm thickness inside a base steel sheet.
−2.5≤[P]/[Cr]−[Mg]×100≤6.5  [Equation 1]
(In Equation 1, [P], [Cr], and [Mg] respectively represent a content (by wt %) of P, Cr, and Mg).

A grain-oriented electrical steel sheet for a stacked transformer core. The steel sheet having a sheet thickness t, where t and an iron loss deterioration ratio obtained by subjecting the steel sheet under elliptic magnetization satisfy the following relations: (i) when t≤0.20 mm, the iron loss deterioration ratio is 85% or less; (ii) when 0.20 mm<t<0.27 mm, the iron loss deterioration ratio is 80% or less; and (iii) when 0.27 mm≤t, the iron loss deterioration ratio is 75% or less. The iron loss deterioration ratio is calculated from ((W.sub.A−W.sub.B)/W.sub.B)×100, where W.sub.A is iron loss under 50 Hz elliptic magnetization of 1.7 T in a rolling direction and 1.0 T in a direction orthogonal to the rolling direction, and W.sub.B is iron loss under 50 Hz alternating magnetization of 1.7 T in the rolling direction.

A grain-oriented electrical steel sheet for a stacked transformer core. The steel sheet having a sheet thickness t, where t and an iron loss deterioration ratio obtained by subjecting the steel sheet under elliptic magnetization satisfy the following relations: (i) when t≤0.20 mm, the iron loss deterioration ratio is 85% or less; (ii) when 0.20 mm<t<0.27 mm, the iron loss deterioration ratio is 80% or less; and (iii) when 0.27 mm≤t, the iron loss deterioration ratio is 75% or less. The iron loss deterioration ratio is calculated from ((W.sub.A−W.sub.B)/W.sub.B)×100, where W.sub.A is iron loss under 50 Hz elliptic magnetization of 1.7 T in a rolling direction and 1.0 T in a direction orthogonal to the rolling direction, and W.sub.B is iron loss under 50 Hz alternating magnetization of 1.7 T in the rolling direction.

A method for manufacturing a non-oriented electrical steel sheet includes a step of obtaining a hot-rolled steel sheet by performing hot rolling on a steel material having a predetermined chemical composition, a step of performing first cold rolling on the hot-rolled steel sheet, and a step of performing first annealing after the first cold rolling. A final pass of finish rolling is performed in a temperature range equal to or higher than an Ar1 temperature, and cooling of which an average cooling rate is in a range of 50 to 500° C./sec is started in 0.1 sec from completion of rolling of the final pass of the finish rolling and is performed up to a temperature range higher than 250° C. and equal to or lower than 700° C.