Abstract: A soft magnetic material that is sheet-shaped or foil-shaped and has a high saturation magnetic flux density, contains iron, carbon, and nitrogen, and includes a martensite containing carbon and nitrogen, and ?-Fe, wherein the ?-Fe includes a nitrogen-containing phase. The soft magnetic material is produced by steps of heating an iron-based material that is sheet-shaped or foil-shaped, carburizing the iron-based material with a carburizing gas, dispersing a granular carbide in ?-Fe in the iron-based material at a temperature equal to or lower than a eutectoid temperature, transforming the ?-Fe into ?-Fe at a temperature higher than the eutectoid temperature, diffusing nitrogen into the ?-Fe using a nitrogen supply gas to form ?-Fe—N—C, and rapidly heating and then rapidly cooling the ?-Fe—N—C to transform the ?-Fe—N—C into a martensite. The result is a thermally stable soft magnetic material having a saturation magnetic flux density higher than that of pure iron.

Abstract: An object of the present invention is to provide a ball screw having a structure in which a screw shaft and a nut satisfy required performance and having improved durability, a method for manufacturing the ball screw, a power steering device, and a method for manufacturing the power steering device. A ball screw according to the present invention includes: a nut made of a steel substrate having an inner peripheral surface on which a female screw is formed; a screw shaft that is combined with the nut and is made of a steel substrate having an outer peripheral surface on which a male screw facing the female screw is formed; and a plurality of balls arranged between the female screw and the male screw. A surface of the nut in contact with the ball and a surface of the screw shaft in contact with the ball each have carburized layers. A carbon concentration in the carburized layer of the nut is higher than a carbon concentration in the carburized layer of the screw shaft.

Abstract: The present invention provides a nitriding treatment method for forming a compound layer of ? phase (Fe2-3N) and ?? phase (Fe4N) iron nitride excellent in wear durability in a steel material, from which a sliding member is formed, by short treatment, with a high thermal efficiency, with a reduced amount of used nitriding gas, and with a low environmental load. The nitriding treatment method of the present invention includes heating a sliding member made of a steel material at a temperature of 600° C. to 700° C. for a time of 1 to 25 minutes under an atmosphere of nitriding gas through high frequency induction heating or resistive heating, to form a compound layer of ? phase (Fe2-3N) and ?? phase (Fe4N) iron nitride, the compound layer having a nitrogen content of higher than 4.5%, in a surface layer portion of the sliding member.

Abstract: An object of the present invention is to provide a ball screw having a structure in which a screw shaft and a nut satisfy required performance and having improved durability, a method for manufacturing the ball screw, a power steering device, and a method for manufacturing the power steering device. A ball screw according to the present invention includes: a nut made of a steel substrate having an inner peripheral surface on which a female screw is formed; a screw shaft that is combined with the nut and is made of a steel substrate having an outer peripheral surface on which a male screw facing the female screw is formed; and a plurality of balls arranged between the female screw and the male screw. A surface of the nut in contact with the ball and a surface of the screw shaft in contact with the ball each have carburized layers. A carbon concentration in the carburized layer of the nut is higher than a carbon concentration in the carburized layer of the screw shaft.

Abstract: A soft magnetic material that is sheet-shaped or foil-shaped and has a high saturation magnetic flux density, contains iron, carbon, and nitrogen, and includes a martensite containing carbon and nitrogen, and ?-Fe, wherein the ?-Fe includes a nitrogen-containing phase. The soft magnetic material is produced by steps of heating an iron-based material that is sheet-shaped or foil-shaped, carburizing the iron-based material with a carburizing gas, dispersing a granular carbide in ?-Fe in the iron-based material at a temperature equal to or lower than a eutectoid temperature, transforming the ?-Fe into ?-Fe at a temperature higher than the eutectoid temperature, diffusing nitrogen into the ?-Fe using a nitrogen supply gas to form ?-Fe—N—C, and rapidly heating and then rapidly cooling the ?-Fe—N—C to transform the ?-Fe—N—C into a martensite. The result is a thermally stable soft magnetic material having a saturation magnetic flux density higher than that of pure iron.

Abstract: For providing a structural material having improved fatigue strength and abrasion resistance, provided is a structural material containing iron and carbon, including: a first layer formed of pearlite; a second layer formed of a mixed phase of martensite and a carbide; and a third layer formed of a carbide, in order from a center to a surface of the structural material. The carbide of the third layer is represented by MC (where M is one element among Ti, V, Nb, Mo, Ta, and W), and the structural material has a concentration gradient in which an M element concentration is decreased from the surface to the center of the structural material.

Abstract: In a water jet peening apparatus, a high-pressure under-water pump is installed on an upper end of a casing and an injection nozzle drive mechanism equipped with an injection nozzle is attached to the casing. A high-pressure hose whose one end is connected to the high-pressure under-water pump is disposed in the casing and the other end of the high-pressure hose is connected to the injection nozzle. The casing is seated at an upper end of a control rod drive mechanism housing and the high-pressure under-water pump is driven. The high-pressure water pressurized by the high-pressure under-water pump is supplied to the injection nozzle through the high-pressure hose in the casing and is jetted toward the weld portion between the control rod drive mechanism housing and a stub tube. The time required for a water jet peening operation can be shortened.

Abstract: The object of the present invention is to provide a sodium-sulfur battery suitable for use in an electric power storage system and an electric vehicle, wherein said battery permits reconciling improvement in battery efficiency with enlargement in battery capacity.