An electrical steel sheet (300) is formed such that centerlines of four magnetic poles (salient poles) of a rotor core (111) coincide with a direction of easy magnetization (ED1) or (ED2). In addition, the electrical steel sheets (300) are laminated such that the directions of easy magnetization (ED1) and (ED2) are aligned.

The present invention is a stator core (21) including a plurality of split cores (30), in which the plurality of split cores (30) are configured by laminating core pieces (40) made of an electrical steel sheet, the electrical steel sheet is a predetermined electrical steel sheet, and, in the core pieces (40) of at least one split core (30) in the plurality of split cores (30), the radial directions of teeth (41) and extension directions of core backs (42) are all along a direction in which magnetic characteristics of the electrical steel sheet are excellent.

The present invention is a stator core (21) including a plurality of split cores (30), in which the plurality of split cores (30) are configured by laminating core pieces (40) made of an electrical steel sheet, the electrical steel sheet is a predetermined electrical steel sheet, and, in the core pieces (40) of at least one split core (30) in the plurality of split cores (30), the radial directions of teeth (41) and extension directions of core backs (42) are all along a direction in which magnetic characteristics of the electrical steel sheet are excellent.

Provided is an alloy having a high strength and a low thermal expansion coefficient. The alloy according to the present disclosure includes a chemical composition containing, in mass %: C: 0.10% or less, Si: 0.50% or less, Mn: 0.15 to 0.60%, P: 0.015% or less, 5: 0.0030% or less, Ni: 30.0 to 40.0%, Cr: 0.50% or less, Mo: 0.50% or less, Co: 0.250% or less, Al: 0.0150% or less, Ca: 0.0050% or less, Mg: 0.0300% or less, N: 0.0100% or less, O: 0.0300% or less, Pb: 0.0040% or less, and Zn: 0.020% or less, one or more elements selected from the group consisting of Nb: 0 to less than 0.145%, Ti: 0 to less than 0.145%, and. V: 0 to less than 0.145%: 0.015 to less than 0.145% in total, with the balance being Fe and impurities, and satisfying Formula (1).

(Nb+3×Ti+V)/(C+N)≤6.00   (1)

Provided is an alloy having a high strength and a low thermal expansion coefficient. The alloy according to the present disclosure includes a chemical composition containing, in mass %: C: 0.10% or less, Si: 0.50% or less, Mn: 0.15 to 0.60%, P: 0.015% or less, 5: 0.0030% or less, Ni: 30.0 to 40.0%, Cr: 0.50% or less, Mo: 0.50% or less, Co: 0.250% or less, Al: 0.0150% or less, Ca: 0.0050% or less, Mg: 0.0300% or less, N: 0.0100% or less, O: 0.0300% or less, Pb: 0.0040% or less, and Zn: 0.020% or less, one or more elements selected from the group consisting of Nb: 0 to less than 0.145%, Ti: 0 to less than 0.145%, and. V: 0 to less than 0.145%: 0.015 to less than 0.145% in total, with the balance being Fe and impurities, and satisfying Formula (1).

(Nb+3×Ti+V)/(C+N)≤6.00   (1)

Provided is a hot rolled steel sheet comprising a predetermined composition wherein the hot rolled steel sheet comprises ferrite with an average orientation difference in the same grain of 0.5 to 5.0° in 30 to 70 vol %, the ferrite and martensite in a total of 90 vol % or more, and a balance microstructure of 10 vol % or less, has an average grain size of the ferrite of 0.5 to 5.0 μm, and has an average grain size of the martensite and the balance microstructure of 1.0 to 10 μm. Provided is a method for producing a hot rolled steel sheet comprising rolling where two or more consecutive passes of rolling including a final pass are performed under conditions of a rolling temperature: A point or more and less than Ae.sub.3 point, a strain rate: 1.0 to 50/sec, and a time between passes: within 10 seconds and where a total strain amount of all passes satisfying the conditions is 1.4 to 4.0, cooling by a 20° C./sec or more average cooling rate, and coiling the steel sheet at room temperature or more and less than 300° C.

Provided is a hot rolled steel sheet comprising a predetermined composition wherein the hot rolled steel sheet comprises ferrite with an average orientation difference in the same grain of 0.5 to 5.0° in 30 to 70 vol %, the ferrite and martensite in a total of 90 vol % or more, and a balance microstructure of 10 vol % or less, has an average grain size of the ferrite of 0.5 to 5.0 μm, and has an average grain size of the martensite and the balance microstructure of 1.0 to 10 μm. Provided is a method for producing a hot rolled steel sheet comprising rolling where two or more consecutive passes of rolling including a final pass are performed under conditions of a rolling temperature: A point or more and less than Ae.sub.3 point, a strain rate: 1.0 to 50/sec, and a time between passes: within 10 seconds and where a total strain amount of all passes satisfying the conditions is 1.4 to 4.0, cooling by a 20° C./sec or more average cooling rate, and coiling the steel sheet at room temperature or more and less than 300° C.

Provided is an electric resistance welded steel pipe or tube having excellent fatigue durability after rapid and short-time heating quenching treatment. An electric resistance welded steel pipe or tube comprises: a base metal being a steel sheet having a specific chemical composition and an electric resistance weld portion having a bond width of 40×10.sup.−6 m or more and 120×10.sup.−6 m or less, wherein C.sub.0-C.sub.1 is 0.05 mass % or less, where C.sub.0-C.sub.1 is a difference between C.sub.1 in mass % which is a minimum C content of the electric resistance weld portion and C.sub.0 in mass % which is a C content of the steel sheet, and a depth of a total decarburized layer in each of an inner surface layer and an outer surface layer of the electric resistance welded steel pipe or tube is 50×10.sup.−6 m or less.

Provided is an electric resistance welded steel pipe or tube having excellent fatigue durability after rapid and short-time heating quenching treatment. An electric resistance welded steel pipe or tube comprises: a base metal being a steel sheet having a specific chemical composition and an electric resistance weld portion having a bond width of 40×10.sup.−6 m or more and 120×10.sup.−6 m or less, wherein C.sub.0-C.sub.1 is 0.05 mass % or less, where C.sub.0-C.sub.1 is a difference between C.sub.1 in mass % which is a minimum C content of the electric resistance weld portion and C.sub.0 in mass % which is a C content of the steel sheet, and a depth of a total decarburized layer in each of an inner surface layer and an outer surface layer of the electric resistance welded steel pipe or tube is 50×10.sup.−6 m or less.

The steel sheet of the present invention has a steel microstructure containing, in area fraction, martensite: from 20% to 100%, ferrite: from 0% to 80%, and another metal phase: 5% or less, and in which a ratio of a dislocation density in metal phases on a surface of the steel sheet to a dislocation density in the metal phases in a thicknesswise central portion of the steel sheet is from 30% to 80%. The maximum amount of warpage of the steel sheet when the steel sheet is sheared to a length of 1 m in a rolling direction is 15 mm or less.