To provide a piston ring excellent in thermal setting resistance, and also excellent in side surface wear resistance even under such a high-temperature high-pressure environment as to be more than 300° C. and up to 400° C., the base metal of the piston ring is a steel containing, by mass %, C: 0.30 to 0.65%, Si: 0.80 to 1.20%, Mn: 0.20 to 0.60%, Cr: 4.50 to 5.70%, Cu: 0.01 to 0.5%, and at least one of Mo, V, W, and Co: 0.2 to 5.4%.

Provides is a non-oriented electrical steel sheet suitable for use in a rotor of an IPM motor that has excellent magnetic flux density B.sub.50 and high-frequency iron loss properties, high tensile strength and fatigue strength, and little variation in tensile strength. The non-oriented electrical steel sheet has a predetermined steel sheet chemical composition and a microstructure in which a ratio of non-recrystallized microstructure is 5% or more and 70% or less and the number of inclusion having a diameter of 5 μm or more is not more than 5 counts/mm.sup.2.

This hot-rolled steel sheet has a predetermined chemical composition, in a microstructure at a ¼ position of a sheet thickness in a sheet thickness direction from a surface, a primary phase is bainite, a secondary phase is martensite or a martensite-austenite mixed phase, an average grain size of the secondary phase is 1.5 μm or less, an average grain size of particles having grain diameters that are largest 10% or less out of all particles in the secondary phase is 2.5 μm or less, a pole density in a (110)<112> orientation is 3.0 or less, and, in a microstructure from the surface to a 1/16 position of the sheet thickness in the sheet thickness direction from the surface, a pole density in a (110)<1-11> orientation is 3.0 or less.

The present invention relates to a method for manufacturing a high strength and high toughness steel material which is mainly used at an extremely low temperature and used in various parts of ships for LNG transport and LNG fuel vehicles.

The present invention relates to a method for manufacturing a high strength and high toughness steel material which is mainly used at an extremely low temperature and used in various parts of ships for LNG transport and LNG fuel vehicles.

A mechanical watch or measurement instrument having metallic parts, wherein each part of the mechanical watch mechanism has a relative magnetic permeability of less than 1.01.

A mechanical watch or measurement instrument having metallic parts, wherein each part of the mechanical watch mechanism has a relative magnetic permeability of less than 1.01.

Provided herein is a high-strength seamless steel pipe, and a method for manufacturing same. A high-strength seamless steel pipe of the present invention has a yield strength of 758 MPa or more, and a K.sub.ILIMIT value of 23.0 MPa√m or more as an evaluation index of sulfide stress corrosion cracking resistance.

In the present invention, provided is a steel sheet having a predetermined chemical composition and a metallographic structure, in which A/B, which is a ratio of a length A of an interface between epitaxial ferrite and ferrite to a length B of an interface between the epitaxial ferrite and martensite in a cross section that is along a rolling direction and perpendicular to a surface of the steel sheet at a position of ¼ of a sheet thickness from the surface of the steel sheet is more than 1.5, a ratio of a major axis to a minor axis of the martensite is 5.0 or more, and a tensile strength is 980 MPa or more.

In the present invention, provided is a steel sheet having a predetermined chemical composition and a metallographic structure, in which A/B, which is a ratio of a length A of an interface between epitaxial ferrite and ferrite to a length B of an interface between the epitaxial ferrite and martensite in a cross section that is along a rolling direction and perpendicular to a surface of the steel sheet at a position of ¼ of a sheet thickness from the surface of the steel sheet is more than 1.5, a ratio of a major axis to a minor axis of the martensite is 5.0 or more, and a tensile strength is 980 MPa or more.