A method for treating a part made of ferrous metal includes a nitriding operation forming on the part a combination layer having a thickness of between 5 and 30 μm, and a diffusion region, arranged beneath and in contact with the combination layer, having a thickness of between 100 μm and 500 μm. The method also includes an operation of quenching the part by high-frequency induction, over an induction depth that is greater than or equal to 0.5 mm, thereby hardening the part. The resulting part has a surface hardness greater than or equal to 50 HRC, a hardness of the combination layer greater than or equal to 400 HV0.05, and a hardness of the part greater than or equal to 500 HV0.05 at a depth of 500 μm. The high-frequency induction quenching operation is performed without the application of a protective film on the part prior to the induction quenching operation.

A method for producing a sintered component, in particular an annular sintered component, with a toothing, having teeth with tooth roots, tooth tips and tooth flanks, includes the steps of pressing a powder to form a green compact, sintering the green compact, and hardening the sintered component, wherein after sintering, the tooth flanks and possibly the tooth tips are post-compacted and subsequently undergo post-processing by machining, and wherein a transition region between the tooth flanks and the tooth roots has an undercut design, and post-compaction of the tooth flanks is carried out only up to this transition region.

A method for producing a sintered component, in particular an annular sintered component, with a toothing, having teeth with tooth roots, tooth tips and tooth flanks, includes the steps of pressing a powder to form a green compact, sintering the green compact, and hardening the sintered component, wherein after sintering, the tooth flanks and possibly the tooth tips are post-compacted and subsequently undergo post-processing by machining, and wherein a transition region between the tooth flanks and the tooth roots has an undercut design, and post-compaction of the tooth flanks is carried out only up to this transition region.

A hybrid method of surface hardening metallic components using a combination of chemical modification achieved through additive manufacturing and/or diffusion-based processing with transformation-based processing using a high energy density heat source. The hybrid process results in increased surface hardness and/or increased average case hardness and/or increased case depth compared to either treatment individually.

A lumen stent preform is provided using a plasma nitriding technology, a preparation method thereof, a method for preparing a lumen stent by using the preform, and a lumen stent obtained according to the method. The preform is manufactured by using pure iron or an iron alloy containing no strong nitrogen compound, has a hardness of 160-250HV0.05/10, and has a microstructure that is a deformed structure having a grain size scale greater than or equal to 9 or a deformed structure after cold machining. Alternatively, the preform is an iron alloy containing a strong nitrogen compound, and has a microstructure that is a deformed structure having a grain size scale greater than or equal to 9 or a deformed structure after cold machining. The lumen stem preform meets the requirements of a conventional stent for radial strength and plasticity, so that plasma nitriding is applicable to commercial preparation of a lumen stent.

A medical instrument with excellent operability is provided. The medical instrument includes stick-shaped extra-narrow metal members. The extra-narrow member has a hardened layer formed on the surface thereof without losing flexibility.

A hot-rolled steel sheet for nitriding or a cold-rolled steel sheet for nitriding, in which a dislocation density within 50 μm in the sheet thickness direction from the surface is not less than 2.0 times nor more than 10.0 times as compared to a dislocation density at the position of ¼ in the sheet thickness direction; and a method of manufacturing the same. The manufacturing method comprises, on a hot-rolled steel sheet or a cold-rolled steel sheet, performing pickling, and then performing skin pass rolling under the condition that a reduction ratio is 0.5 to 5.0% and FIT, defined as a ratio of a line load F (kg/mm) of a rolling mill load divided by a sheet width of the steel sheet and a load T (kg/mm.sup.2) per unit area to be applied in the longitudinal direction of the steel sheet, is 8000 or more.

A hot-rolled steel sheet for nitriding or a cold-rolled steel sheet for nitriding, in which a dislocation density within 50 μm in the sheet thickness direction from the surface is not less than 2.0 times nor more than 10.0 times as compared to a dislocation density at the position of ¼ in the sheet thickness direction; and a method of manufacturing the same. The manufacturing method comprises, on a hot-rolled steel sheet or a cold-rolled steel sheet, performing pickling, and then performing skin pass rolling under the condition that a reduction ratio is 0.5 to 5.0% and FIT, defined as a ratio of a line load F (kg/mm) of a rolling mill load divided by a sheet width of the steel sheet and a load T (kg/mm.sup.2) per unit area to be applied in the longitudinal direction of the steel sheet, is 8000 or more.

A steel material for nitriding has a composition comprising, by mass percent, C: more than 0.15% and not more than 0.35%, Si≦0.20%, Mn: 0.10 to 2.0%, P≦0.030%, S≦0.050%, Cr: 0.80 to 2.0%, V: 0.10 to 0.50%, Al: 0.01 to 0.06%, N≦0.0080%, O≦0.0030%, and optionally one or more elements of Mo, Cu, Ni, Ti, Nb, Zr, Pb, Ca, Bi, Te, Se and Sb, the balance being Fe and impurities. The composition satisfies the conditions of [20≦(669.3×log.sub.eC−1959.6×log.sub.eN−6983.3)×(0.067×Mo+0.147×V)≦80] and [140×Cr+125×Al+235×V≧160]. The microstructure is a ferritic-pearlitic structure, a ferritic-bainitic structure, or a ferritic-pearlitic-bainitic structure. The area fraction of ferrite is 20% or more and the precipitate content of V is 0.10% or less.

A steel material for nitriding has a composition comprising, by mass percent, C: more than 0.15% and not more than 0.35%, Si≦0.20%, Mn: 0.10 to 2.0%, P≦0.030%, S≦0.050%, Cr: 0.80 to 2.0%, V: 0.10 to 0.50%, Al: 0.01 to 0.06%, N≦0.0080%, O≦0.0030%, and optionally one or more elements of Mo, Cu, Ni, Ti, Nb, Zr, Pb, Ca, Bi, Te, Se and Sb, the balance being Fe and impurities. The composition satisfies the conditions of [20≦(669.3×log.sub.eC−1959.6×log.sub.eN−6983.3)×(0.067×Mo+0.147×V)≦80] and [140×Cr+125×Al+235×V≧160]. The microstructure is a ferritic-pearlitic structure, a ferritic-bainitic structure, or a ferritic-pearlitic-bainitic structure. The area fraction of ferrite is 20% or more and the precipitate content of V is 0.10% or less.