Abstract: Provided is a bearing steel capable of exhibiting excellent cold workability in cold working that follows spheroidizing annealing and also capable of ensuring excellent abrasion resistance and rolling fatigue characteristics as a bearing member or the like. The bearing steel contains C: 0.9 to 1.10%, Si: 0.05 to 0.49%, Mn: 0.1 to 1.0%, P: not more than 0.05% (excluding 0%), S: not more than 0.05% (excluding 0%), Cr: 0.03 to 0.40%, Al: not more than 0.05% (excluding 0%), N: 0.002 to 0.025%, Ti: not more than 0.0030% (excluding 0%), and O: not more than 0.0025% (excluding 0%), with the remainder being iron and unavoidable impurities. The average aspect ratio of cementite is not more than 2.00, the average circle-equivalent diameter of cementite is 0.35 to 0.6 ?m, and the number density of cementite having a circle-equivalent diameter of not less than 0.13 ?m is not less than 0.45/?m2.

Abstract: Bearing steel material according to the present invention has: a properly adjusted chemical composition; an average chemical composition of oxide-inclusions which comprises 10 to 45% of CaO, 20 to 45% of Al2O3, 30 to 50% of SiO2, up to 15% (exclusive of 0) of MnO, and 3 to 10% of MgO, with the balance being unavoidable impurities; a maximum major axis diameter of the oxide inclusions in a longitudinal section of the steel material of 20 ?m or less; and a spheroidal cementite structure.

Abstract: Disclosed is a steel for machine structural use including 0.05-0.8% of C, 0.03-2% of Si, 0.2-1.8% of Mn, 0.1-0.5% of Al, 0.0005-0.008% of B, and 0.002-0.015% of N, and including 0.03% of P or less (excluding 0%), 0.03% of S or less (excluding 0%), and 0.002% of O or less (excluding 0%), with the remainder comprising iron and unavoidable impurities. The ratio of BN/AlN precipitated in the steel is 0.020-0.2. Also disclosed is a case hardened steel component in which the ratio of BN/AlN deposited on the carburized or carbonitrided component surface is 0.01 or less and a manufacturing method for same. The steel for machine structural use exhibits excellent machinability in continuous cutting at high speeds using cemented carbide tools, and in interrupted cutting at low speeds using high-speed steel tools, as well as excellent impact performance, even after being subjected to a heat treatment such as quenching and tempering.

Abstract: A case hardened steel with excellent cold forgeability and excellent impact properties after case hardening processing contains C, Si, Mn, S, Cr, Al, Ti, Nb, B, and N, with the balance being iron and unavoidable impurities. Of precipitates containing Ti and/or Nb, precipitates having a size of not less than 20 ?m2 are at a number density of not more than 1.0/mm2. Of precipitates containing Ti and/or Nb, precipitates having a size of more than 5 ?m2 and less than 20 ?m2 and containing Mn and S are at a number density of more than 0.7/mm2 and not more than 3.0/mm2. The ferrite fraction is more than 77% by area.

Abstract: Provided is a steel for machine structural use which has excellent machinability (particularly, with respect to tool life) for both intermittent cutting with a high-speed steel tool and continuous cutting with a cemented carbide tool while maintaining strength properties required of the steel for machine structural use. Specifically, the steel for machine structural use contains C: 0.05-0.9 mass %, Si: 0.03-2 mass %, Mn: 0.2-1.8 mass %, P: 0.03 mass % or less, S: 0.03 mass % or less, Al: 0.1-0.5 mass %, N: 0.002-0.017 mass %, and O: 0.003 mass % or less, and contains one or more selected from a group consisting of Ti: 0.05 mass % or less (excluding 0 mass %) and B: 0.008 mass % or less (excluding 0 mass %), with the remainder being iron and unavoidable impurities, and satisfies all of the following inequalities (1)-(3) below: (1): [N]?0.3[Ti]?1.4[B]<(0.0004/[Al])?0.002; (2): [Ti]?[N]/0.3<0.005; and (3): [B]?([N]?0.3[Ti])/1.4<0.003 when [Ti]?[N]/0.3<0 and [B]<0.003 when [Ti]?[N]/0.3?0.

Abstract: Bearing steel material according to the present invention has: a properly adjusted chemical composition; an average chemical composition of oxide-inclusions which comprises 10 to 45% of CaO, 20 to 45% of Al2O3, 30 to 50% of SiO2, up to 15% (exclusive of 0) of MnO, and 3 to 10% of MgO, with the balance being unavoidable impurities; a maximum major axis diameter of the oxide inclusions in a longitudinal section of the steel material of 20 ?m or less; and a spheroidal cementite structure.

Abstract: Provided is a bearing steel capable of exhibiting excellent cold workability in cold working that follows spheroidizing annealing and also capable of ensuring excellent abrasion resistance and rolling fatigue characteristics as a bearing member or the like. The bearing steel contains C: 0.9 to 1.10%, Si: 0.05 to 0.49%, Mn: 0.1 to 1.0%, P: not more than 0.05% (excluding 0%), S: not more than 0.05% (excluding 0%), Cr: 0.03 to 0.40%, Al: not more than 0.05% (excluding 0%), N: 0.002 to 0.025%, Ti: not more than 0.0030% (excluding 0%), and 0: not more than 0.0025% (excluding 0%), with the remainder being iron and unavoidable impurities. The average aspect ratio of cementite is not more than 2.00, the average circle-equivalent diameter of cementite is 0.35 to 0.6 ?m, and the number density of cementite having a circle-equivalent diameter of not less than 0.13 ?m is not less than 0.45/?m2.

Abstract: A case hardened steel with excellent cold forgeability and excellent impact properties after case hardening processing contains C, Si, Mn, S, Cr, Al, Ti, Nb, B, and N, with the balance being iron and unavoidable impurities. Of precipitates containing Ti and/or Nb, precipitates having a size of not less than 20 ?m2 are at a number density of not more than 1.0/mm2. Of precipitates containing Ti and/or Nb, precipitates having a size of more than 5 ?m2 and less than 20 ?m2 and containing Mn and S are at a number density of more than 0.7/mm2 and not more than 3.0/mm2. The ferrite fraction is more than 77% by area.

Abstract: Disclosed is a steel for machine structural use including 0.05-0.8% of C, 0.03-2% of Si, 0.2-1.8% of Mn, 0.1-0.5% of Al, 0.0005-0.008% of B, and 0.002-0.015% of N, and including 0.03% of P or less (excluding 0%), 0.03% of S or less (excluding 0%), and 0.002% of 0 or less (excluding 0%), with the remainder comprising iron and unavoidable impurities. The ratio of BN/A1N precipitated in the steel is 0.020-0.2. Also disclosed is a case hardened steel component in which the ratio of BN/AlN deposited on the carburized or carbonitrided component surface is 0.01 or less and a manufacturing method for same. The steel for machine structural use exhibits excellent machinability in continuous cutting at high speeds using cemented carbide tools, and in interrupted cutting at low speeds using high-speed steel tools, as well as excellent impact performance, even after being subjected to a heat treatment such as quenching and tempering.

Abstract: The present invention provides a steel for machine and structural use which is capable of maintaining mechanical characteristics such as strength by reducing a S content as well as of exhibiting excellent machinability (particularly tool life) in intermittent cutting (such as hobbing) with the high speed tool, and a method useful for producing the steel for machine and structural use. The steel for machine and structural use according to the invention secures 0.002% or more of solute N in the steel and has a chemical composition which is appropriately adjusted and satisfies a relationship of the following expression (1): (0.1×[Cr]+[Al])/[O]?150 . . . (1), in which [Cr], [Al], and [0] represent a Cr content (mass %), an Al content (mass %), and an O content (mass %), respectively.

Abstract: Provided is a steel for machine structural use which has excellent machinability (particularly, with respect to tool life) for both intermittent cutting with a high-speed steel tool and continuous cutting with a cemented carbide tool while maintaining strength properties required of the steel for machine structural use. Specifically, the steel for machine structural use contains C: 0.05-0.9 mass %, Si: 0.03-2 mass %, Mn: 0.2-1.8 mass %, P: 0.03 mass % or less, S: 0.03 mass % or less, Al: 0.1-0.5 mass %, N: 0.002-0.017 mass %, and O: 0.003 mass % or less, and contains one or more selected from a group consisting of Ti: 0.05 mass % or less (excluding 0 mass %) and B: 0.008 mass % or less (excluding 0 mass %), with the remainder being iron and unavoidable impurities, and satisfies all of the following inequalities (1)-(3) below: (1): [N]?0.3[Ti]?1.4[B]<(0.0004/[Al])?0.002; (2): [Ti]?[N]/0.3<0.005; and (3): [B]?([N]?0.3[Ti])/1.4<0.003 when [Ti]?[N]/0.3<0 and [B]<0.003 when [Ti]?[N]/0.3?0.

Abstract: The present invention provides a steel for machine and structural use which is capable of maintaining mechanical characteristics such as strength by reducing a S content as well as of exhibiting excellent machinability (particularly tool life) in intermittent cutting (such as hobbing) with the high speed tool, and a method useful for producing the steel for machine and structural use. The steel for machine and structural use according to the invention secures 0.002% or more of solute N in the steel and has a chemical composition which is appropriately adjusted and satisfies a relationship of the following expression (1): (0.1×[Cr]+[Al])/[O]?150 . . . (1), in which [Cr], [Al], and [0] represent a Cr content (mass %), an Al content (mass %), and an O content (mass %), respectively.

Abstract: A wire rod steel superior in straightness, after being subjected to cold drawing. This wire rod steel comprises: C: 0.15 mass % or less (not including 0 mass %), Si: 0.05 mass % or less (including 0 mass %), Mn: 0.3-2 mass %, P: 0.2 mass % or less (including 0 mass %), S: 0.08-0.5 mass %, Al: 0.05 mass % or less (including 0 mass %), N: 0.01 mass % or less (not including 0 mass %), inevitable impurities and Fe as the balance. Its ferrite grain size number of the wire rod steel is No. 11 or less according to ISO 643.