Abstract: Provided are a roughly-shaped steel material for a nitrided part, and a nitrided part obtained by nitriding the roughly-shaped steel material for a nitrided part, having a determined chemical composition, in which the portion with a diameter or width ranging from 60 to 130 mm of the roughly-shaped steel material for a nitrided part has a microstructure at a depth of 14.5 mm from a surface including, in terms of area fraction: tempered martensite and tempered bainite in total: from 70 to 100%; remaining austenite: from 0 to 5%; and a balance: ferrite and perlite; and has a microstructure at a depth of 15 mm or more from the surface including, in terms of area fraction: tempered martensite and tempered bainite in total: from 0 to less than 50%; remaining austenite: from 0 to 5%; and a balance: ferrite and perlite.

Abstract: A crankshaft with improved seizure resistance is provided. A crankshaft having journals 11 and pins 12 includes a compound layer containing iron and nitrogen on its surface, wherein, in the compound layer, for both the journals 11 and pins 12, the porosity area ratio of the thinner one of a region from the surface to a depth of 3.0 ?m and a region across the total thickness of the compound layer is not higher than 10.0%, and both the journals 11 and pins 12 have such a surface geometry that the arithmetical mean deviation of the primary profile, Pa, is not larger than 0.090 ?m.

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: Provided are a roughly-shaped steel material for a nitrided part, and a nitrided part obtained by nitriding the roughly-shaped steel material for a nitrided part, having a determined chemical composition, in which the portion with a diameter or width ranging from 60 to 130 mm of the roughly-shaped steel material for a nitrided part has a microstructure at a depth of 14.5 mm from a surface including, in terms of area fraction: tempered martensite and tempered bainite in total: from 70 to 100%; remaining austenite: from 0 to 5%; and a balance: ferrite and perlite; and has a microstructure at a depth of 15 mm or more from the surface including, in terms of area fraction: tempered martensite and tempered bainite in total: from 0 to less than 50%; remaining austenite: from 0 to 5%; and a balance: ferrite and perlite.

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 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 component has a chemical composition consisting of, by mass percent, C: 0.07-0.14%, Si: 0.10-0.30%, Mn: 0.4-1.0%, S: 0.005-0.030%, Cr: 1.0-1.5%, Mo: ?0.05% (including 0%), Al: 0.010% or more to less than 0.10%, V: 0.10-0.25%, optionally at least one element selected from Cu: ?0.30% and Ni: ?0.25%, [0.61Mn+1.11Cr+0.35Mo+0.47V?2.30], and the balance of Fe and impurities. P, N, Ti and O among the impurities are P: ?0.030%, N: ?0.008%, Ti: ?0.005%, and O: ?0.0030%. The nitrided composition is suitable for use as an automobile ring gear. The nitrided component has a surface hardness of 650-900 HV, core hardness being ?150 HV, effective case depth of ?0.15 mm, has excellent bending fatigue strength and surface fatigue strength although the content of Mo is as low as ?0.05% and has a small amount of expansion caused by nitriding.

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: An age-hardenable steel having a composition consisting of: C: 0.05 to 0.20%, Si: 0.01 to 0.50%, Mn: 1.5 to 2.5%, S: 0.005 to 0.08%, Cr: more than 0.50% and not more than 1.6%, Al: 0.005 to 0.05%, V: 0.25 to 0.50%, Mo: 0 to 1.0%, Cu: 0 to 0.3%, Ni: 0 to 0.3%, Ca: 0 to 0.005%, and Bi: 0 to 0.4%, the balance being Fe and impurities. Within the impurities, P?0.03%, Ti<0.005%, and N<0.0080%, and [C+0.3Mn+0.25Cr+0.6Mo?0.68], [C+0.1Si+0.2Mn+0.15Cr+0.35V+0.2Mo?1.05], and [?4.5C+Mn+Cr?3.5V?0.8Mo?0.12]. The steel has hardness before aging of not more than 310 HV. After aging, the fatigue strength is not less than 480 MPa and absorbed energy at 20° C. is not less than 12 J.

Abstract: Age hardenable steel is low in hardness after hot forging, providing a machine part with the desired fatigue strength and yield strength by aging treatment, and high in toughness after aging treatment, comprising C: 0.09 to 0.20%, Si: 0.01 to 0.40%, Mn: 1.5 to 2.5%, S: 0.001 to 0.045%, Cr: over 1.00% to 2.00%, Al: 0.001 to 0.060%, V: 0.22 to 0.55%, N: over 0.0080 to 0.0170%, and a balance of Fe and impurities, where an area rate of bainite structures is 80% or more, an effective V ratio (amount of dissolved V/total amount of V) is 0.9 or more, a P and Ti in the impurities is P: 0.03% or less and Ti: less than 0.005%, and the chemical composition is one where the following F1 is 1.00 or less and the F2 is 0.30 or more: F1=C+0.1×Si+0.2×Mn+0.15×Cr+0.35×V F2=?4.5×C+Mn+Cr?3.

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: Provided is a non-thermal refined soft-nitrided component including chemical composition of a steel material of a base metal containing: in mass %, C: 0.25 to 0.40%; Si: 0.10 to 0.35%; Mn: more than 2.0% to 2.8% or less; N: 0.0030 to 0.0250%; Cu: 0 to 1.0%; Mo: 0 to 0.3%; Ni: 0 to 0.5%; Ti: 0 to 0.020%; and a balance being Fe and impurities, the impurities including P: 0.08% or less; S: 0.10% or less; Al: 0.05% or less; and Cr: less than 0.20%, wherein a Vickers hardness at a position of 0.05 mm from the surface is 400 to 480, a Vickers hardness at a position of 1.0 mm from the surface is 200 or more, and a compound-layer depth at a stress concentrated region is 5 ?m or less. This non-thermal refined soft-nitrided component has an excellent bending straightening property and a high fatigue strength.

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: Age hardening steel excellent in machinability before aging treatment and excellent in fatigue characteristics, toughness, and low cycle fatigue characteristics after aging treatment, that is, age hardening steel containing predetermined amounts of C, Si, Mn, S, Cr, Al, V, Nb, Ca, and REM, limiting contents of P, Ti, and N to predetermined amounts or less, having a balance of Fe and impurities, having an area ratio of bainite structures of 70% or more, and, furthermore, having a chemical composition where F1 expressed by C+0.3×Mn+0.25×Cr is 0.68 or more, F2 expressed by C+0.1×Si+0.2×Mn+0.15×Cr+0.35×V is 0.85 or less, F3 expressed by ?4.5×C+Mn+Cr?3.5×V is 0.00 or more, and F4 expressed by 10×Ca+REM is 0.012 to 0.08, is provided. Note that, the symbols of elements in the formulas showing F1 to F4 mean the contents by mass % of those elements.

Abstract: A nitrided steel member including an iron nitride compound layer formed on a surface of a steel member having predetermined components, wherein: in X-ray diffraction peak intensity IFe4N (111) of a (111) crystal plane of Fe4N and X-ray diffraction peak intensity IFe3N (111) of a (111) crystal plane of Fe3N, which are measured on a surface of the nitrided steel member by X-ray diffraction, an intensity ratio expressed by IFe4N (111)/{IFe4N (111)+IFe3N (111)} is 0.5 or more; Vickers hardness of the iron nitride compound layer is 900 or less, Vickers hardness of a base metal immediately under the iron nitride compound layer is 700 or more, and a difference between the Vickers hardness of the iron nitride compound layer and the Vickers hardness of the base metal is 150 or less; and a thickness of the iron nitride compound layer is 2 to 17 ?m.

Abstract: A nitrided component has a chemical composition consisting of, by mass percent, C: 0.07-0.14%, Si: 0.10-0.30%, Mn: 0.4-1.0%, S: 0.005-0.030%, Cr: 1.0-1.5%, Mo: ?0.05% (including 0%), Al: 0.010% or more to less than 0.10%, V: 0.10-0.25%, optionally at least one element selected from Cu: ?0.30% and Ni: ?0.25%, [0.61Mn+1.11Cr+0.35Mo+0.47V?2.30], and the balance of Fe and impurities. P, N, Ti and O among the impurities are P: ?0.030%, N: ?0.008%, Ti: ?0.005%, and O: ?0.0030%. The nitrided composition is suitable for use as an automobile ring gear. The nitrided component has a surface hardness of 650-900 HV, core hardness being ?150 HV, effective case depth of ?0.15 mm, has excellent bending fatigue strength and surface fatigue strength although the content of Mo is as low as ?0.05% and has a small amount of expansion caused by nitriding.