# US 10,767,252 B2 · Carburized component and method for manufacturing same > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,767,252 B2 - Document ID: US10767252B2 - Status: Granted - Kind: B2 - Application number: 14/895,098 - Filed: 2014-06-03 - Published: 2016-05-05 - Granted: 2020-09-08 - Earliest claimed: 2013-06-05 - Assignees: Daido Steel Co., Ltd. - Applicants: Daido Steel Co., Ltd. - Inventors: Tomohiro Andoh; Naoki Umemori; Toshiyuki Morita; Yasushi Matsumura - Web page: https://patentgrep.com/patent/US10767252B2 ## CPC - C23C 8/34: more than one element being applied in more than one step - C21D 1/06: Surface hardening - C21D 1/773: under reduced pressure or vacuum - C21D 6/002: {containing Cr (C21D6/004 takes precedence)} - C21D 6/005: {containing Mn} - C21D 6/008: {containing Si} - C22C 38/00: Ferrous alloys, e.g. steel alloys (cast-iron alloys C22C37/00) - C22C 38/001: {containing N} - C22C 38/02: containing silicon - C22C 38/04: containing manganese - C22C 38/06: containing aluminium - C22C 38/22: with molybdenum or tungsten - C22C 38/26: with niobium or tantalum - C22C 38/28: with titanium or zirconium - C23C 8/22: of ferrous surfaces - C23C: COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL (making metal-coated products by extrusion B21C23/22; covering with metal by connecting pre-existing layers to articles, see the relevant places, e.g. B21D39/00, B23K; metallising of glass C03C; metallising mortars, concrete, artificial stone, ceramics or natural stone C04B41/00; enamelling of, or applying a vitreous layer to, metals C23D; treating metal surfaces or coating of metals by electrolysis or electrophoresis C25D; single-crystal film growth C30B; by metallising textiles D06M11/83; decorating textiles by locally metallising D06Q1/04) - C21D: MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING (surface treatment of metallic material involving at least one process provided for in class C23 and at least one process covered by this subclass C23F17/00; unidirectional solidification of eutectic materials or unidirectional demixing of eutectoid materials C30B) - C22C: ALLOYS (treatment of alloys C21D, C22F) ## Abstract The present invention provides a carburized part which is formed by processing a steel into a shape of a part and performing a carburizing treatment on the steel, the steel having a composition consisting essentially of, in terms of % by mass: 0.10% to 0.40% of C; 0.05% to 2.00% of Si; 0.30% to 2.00% of Mn; 0.30% to 3.00% of Cr; 0.025% or less of N; and as a pinning particle forming element which forms a pinning particle by nitrification, one or two or more elements selected from: 0.020% to 0.100% of Al; 0.01% to 0.20% of Nb; and 0.005% to 0.20% of Ti, and optionally: 0.80% or less of Mo, with the remainder being Fe and inevitable impurities, in which a crystal grain size number of a surface layer of the part at a depth of 50 μm or less from a surface is greater than 5, and the crystal grain size number of an inner portion of the part at a depth of 3 mm or more from the surface is 5 or less. ## Claims ### Claim 1 A carburized part which is formed by processing a steel into a shape of a part and performing a carburizing treatment on the steel, the steel having a composition consisting essentially of, in terms of % by mass: 0.10% to 0.40% of C; 0.05% to 2.00% of Si; 0.30% to 2.00% of Mn; 0.30% to 3.00% of Cr; 0.025% or less of N; 0 to 0.80% of Mo, and as a pinning particle forming element which forms a pinning particle by nitrification, one or two or more elements selected from: 0.020% to 0.100% of Al; 0.01% to 0.20% of Nb; and 0.005% to 0.20% of Ti, with the remainder being Fe and inevitable impurities, wherein a crystal grain size number of a surface layer of the part at a depth of 50 μm or less from a surface is greater than 5, and the crystal grain size number of an inner portion of the part at a depth of 3 mm or more from the surface is 5 or less, wherein an N concentration in the surface layer of the part is higher than the N concentration in the inner portion of the part, and wherein nitrides of one or two or more elements selected from Al, Nb, or Ti are precipitated in the surface layer of the part at a depth of 50 μm or less from the surface. ### Claim 2 (depends on 1) A method for manufacturing the carburized part according to claim 1, the method comprising: processing a steel into a shape of a part, the steel having a composition consisting essentially of, in terms of % by mass: 0.10% to 0.40% of C; 0.05% to 2.00% of Si; 0.30% to 2.00% of Mn; 0.30% to 3.00% of Cr; 0.025% or less of N; 0 to 0.80% of Mo, and as a pinning particle forming element which forms a pinning particle by nitrification, one or two or more elements selected from: 0.020% to 0.100% of Al; 0.01% to 0.20% of Nb; and 0.005% to 0.20% of Ti, with the remainder being Fe and inevitable impurities; then heating the steel in a treatment furnace at a temperature of A3 point or higher and holding the steel to perform a vacuum carburizing treatment on the steel with a carburizing gas under reduced pressure; controlling a nitriding atmosphere by introducing a nitriding gas into the treatment furnace during the vacuum carburizing treatment, such that a total amount V of nitride particles containing one or two or more of AlN which is a nitride of Al, NbN which is a nitride of Nb, and TiN which is a nitride of Ti in a surface layer at a depth of 50 μm or less from a surface of the part is maintained at a value represented by the following Equation (1) or more during the carburizing treatment; and determining the content of N in the steel such that the total amount V of the nitride particles in an inner portion of the part at a depth of 3 mm or more from the surface is less than the value represented by the following Equation (1) during the carburizing treatment, thereby obtaining a carburized part in which a crystal grain size number of the surface layer of the part is greater than 5 and the crystal grain size number of the inner portion of the part is 5 or less, (3.33×10−5×C+7.33×10−5)×T−(3.58×10−2×C+7.37×10−2) Equation (1) in the Equation (1), C represents a C concentration, and T represents a temperature, provided that the unit of V is % by mass, the unit of C is % by mass, and the unit of T is K.