Abstract: The present invention has as its technical problem the provision of a part excellent in contact fatigue strength or wear resistance in addition to the rotating bending fatigue strength. In the present invention, the contents of the constituents of the steel, in particular C, Mn, Cr, V, and Mo, are adjusted in accordance with the targeted properties and nitrided parts are prepared while controlling the nitriding potential.

Abstract: The present invention has as its technical problem the provision of a part excellent in contact fatigue strength or wear resistance in addition to the rotating bending fatigue strength. In the present invention, the contents of the constituents of the steel, in particular C, Mn, Cr, V, and Mo, are adjusted in accordance with the targeted properties and nitrided parts are prepared while controlling the nitriding potential.

Abstract: A nitrided part having excellent fatigue strength which has predetermined constituents, has structures comprised of ferrite and pearlite, has ferrite grains with an aspect ratio of a ratio of a long axis direction and short axis direction of 4.5 or more present in the entire region at a depth from the surface of the part where stress is expected to concentrate of (?×0.09+0.05) mm or less, and has an average concentration of N of 5000 ppm or more at a surface layer part from the surface down to 200 ?m in the depth direction.

Abstract: A nitrided steel part excellent in bending straightening ability and bending fatigue characteristic enabling reduction of size and decrease of weight of parts or enabling demand for high load capacities to be met, using as a material a steel material containing, by mass %, C: 0.2 to 0.6%, Si: 0.05 to 1.5%, Mn: 0.2 to 2.5%, P: 0.025% or less, S: 0.003 to 0.05%, Cr: 0.05 to 0.5%, Al: 0.01 to 0.05%, and N: 0.003 to 0.025%, and having a balance of Fe and impurities, having formed on the steel surface a compound layer of a thickness 3 ?m or less comprising iron, nitrogen, and carbon and a hardened layer formed below the compound layer, and having an effective hardened layer depth of 160 to 410 ?m.

Abstract: A nitrided steel part excellent in pitting resistance and bending fatigue characteristic enabling reduction of size and decrease of weight of parts or enabling demand for high load capacities to be met, using as a material a steel material containing, by mass %, C: 0.05 to 0.25%, Si: 0.05 to 1.5%, Mn: 0.2 to 2.5%, P: 0.025% or less, S: 0.003 to 0.05%, Cr: over 0.5 to 2.0%, Al: 0.01 to 0.05%, and N: 0.003 to 0.025%, having a balance of Fe and impurities, having formed on the steel surface a compound larger of a thickness 3 ?m or less containing iron, nitrogen, and carbon and a hardened layer formed below the compound layer, and having an effective hardened layer depth of 160 to 410 ?m.

Abstract: A nitrided part and soft nitrided part with excellent wear resistance and pitting resistance and a nitriding method and soft nitriding method are provided, specifically, a nitrided part or soft nitrided part made by a steel material comprising, by mass %, C: 0.05 to 0.3%, Si: 0.05 to 1.5%, Mn: 0.2 to 1.5%, P: 0.025% or less, S: 0.003 to 0.05%, Cr: 0.5 to 2.0%, Al: 0.01 to 0.05%, and N: 0.003 to 0.025% and having a balance of Fe and impurities, wherein, the surface layer comprises a compound layer containing iron, nitrogen, and carbon and a nitrogen diffusion layer positioned below the compound layer, the compound layer comprises an ? single phase, the ? single phase has a thickness of 8 to 30 ?m and a Vicker's hardness of 680 HV or more, and the ? single phase has a volume ratio of pores of less than 10%.

Abstract: A nitrided part excellent in contact fatigue strength plus rotating bending fatigue strength, the nitrided part having a steel material having a predetermined chemical composition as a material, wherein the nitrided part comprises a compound layer formed on the surface of the steel material, the compound layer containing iron, nitrogen, and carbon, a thickness of the compound layer being 3 ?m to less than 20 ?m; a phase structure in the compound layer in a range from the surface down to a depth of 5 ?m contains ?? phases in an area ratio of 50% or more; a pore area ratio in a range from the surface down to a depth of 3 ?m is less than 10%; and a compressive residual stress of the compound layer surface is 500 MPa or more.

Abstract: A nitrided part excellent in bending straightening ability plus rotating bending fatigue strength and a method of production of the same, the nitrided part having a steel material having a predetermined chemical composition as a material, wherein the nitrided part comprises a compound layer formed on the surface of the steel material, the compound layer containing iron, nitrogen, and carbon, and a thickness of the compound layer being 3 ?m to less than 15 ?m; a phase structure in the compound layer in a range from the surface down to a depth of 5 ?m contains ?? phases in an area ratio of 50% or more, a pore area ratio in a range from the surface down to a depth of 3 ?m is less than 10%, and a compressive residual stress of the compound layer surface is 500 MPa or more.

Abstract: A nitrided part having excellent fatigue strength which has predetermined constituents, has structures comprised of ferrite and pearlite, has ferrite grains with an aspect ratio of a ratio of a long axis direction and short axis direction of 4.5 or more present in the entire region at a depth from the surface of the part where stress is expected to concentrate of (?×0.09+0.05) mm or less, and has an average concentration of N of 5000 ppm or more at a surface layer part from the surface down to 200 ?m in the depth direction.

Abstract: A low alloy steel is heated to a temperature ranging from 550 to 620° C., and high KN and low KN value processes are performed for a total process time of A: 1.5 to 10 hours. In the high KN value process, a nitriding potential KNX given by Formula (1): 0.15 to 1.50, the average KNX value KNXave: 0.30 to 0.80, and the process time is X in hours. In the low KN value process, which is performed after the high KN value process, a nitriding potential KNY given by Formula (1): 0.02 to 0.25, the average KNY value KNYave: 0.03 to 0.20, and the process time is Y in hours. Average nitriding potential value KNave determined by Formula (2) ranges from 0.07 to 0.30. KNi=(NH3 partial pressure)/(H2 partial pressure)3/2]??(1) KNave=(X×KNXave+Y×KNYave)/A??(2) where i is X or Y.

Abstract: A nitrided steel part excellent in bending straightening ability and bending fatigue characteristic enabling reduction of size and decrease of weight of parts or enabling demand for high load capacities to be met, using as a material a steel material containing, by mass %, C: 0.2 to 0.6%, Si: 0.05 to 1.5%, Mn: 0.2 to 2.5%, P: 0.025% or less, S: 0.003 to 0.05%, Cr: 0.05 to 0.5%, Al: 0.01 to 0.05%, and N: 0.003 to 0.025%, and having a balance of Fe and impurities, having formed on the steel surface a compound layer of a thickness 3 ?m or less comprising iron, nitrogen, and carbon and a hardened layer formed below the compound layer, and having an effective hardened layer depth of 160 to 410 ?m.

Abstract: A nitrided steel part excellent in pitting resistance and bending fatigue characteristic enabling reduction of size and decrease of weight of parts or enabling demand for high load capacities to be met, using as a material a steel material containing, by mass %, C: 0.05 to 0.25%, Si: 0.05 to 1.5%, Mn: 0.2 to 2.5%, P: 0.025% or less, S: 0.003 to 0.05%, Cr: over 0.5 to 2.0%, Al: 0.01 to 0.05%, and N: 0.003 to 0.025%, having a balance of Fe and impurities, having formed on the steel surface a compound larger of a thickness 3 ?m or less containing iron, nitrogen, and carbon and a hardened layer formed below the compound layer, and having an effective hardened layer depth of 160 to 410 ?m.

Abstract: A nitrided part and soft nitrided part with excellent wear resistance and pitting resistance and a nitriding method and soft nitriding method are provided, specifically, a nitrided part or soft nitrided part made by a steel material comprising, by mass %, C: 0.05 to 0.3%, Si: 0.05 to 1.5%, Mn: 0.2 to 1.5%, P: 0.025% or less, S: 0.003 to 0.05%, Cr: 0.5 to 2.0%, Al: 0.01 to 0.05%, and N: 0.003 to 0.025% and having a balance of Fe and impurities, wherein, the surface layer comprises a compound layer containing iron, nitrogen, and carbon and a nitrogen diffusion layer positioned below the compound layer, the compound layer comprises an ? single phase, the ? single phase has a thickness of 8 to 30 ?m and a Vicker's hardness of 680 HV or more, and the ? single phase has a volume ratio of pores of less than 10%.

Abstract: A low alloy steel is heated to a temperature ranging from 550 to 620° C., and high KN and low KN value processes are performed for a total process time of A: 1.5 to 10 hours. In the high KN value process, a nitriding potential KNX given by Formula (1): 0.15 to 1.50, the average KNX value KNXave: 0.30 to 0.80, and the process time is X in hours. In the low KN value process, which is performed after the high KN value process, a nitriding potential KNY given by Formula (1): 0.02 to 0.25, the average KNY value KNYave: 0.03 to 0.20, and the process time is Y in hours. Average nitriding potential value KNave determined by Formula (2) ranges from 0.07 to 0.30. KNi=(NH3 partial pressure)/(H2 partial pressure)3/2]??(1) KNave=(X×KNXave+Y×KNYave)/A??(2) where i is X or Y.