Abstract: Provided is a steel for a mechanical structure for cold working, which contains C, Si, Mn, P, S, Al and N and in which the metal structure includes pearlite and ferrite, the total areal proportion of pearlite and ferrite relative to the overall structure is 90% or higher, the average circle-equivalent diameter of bcc-Fe crystal grains surrounded by large angle grain boundaries is 5-15 ?m, the average aspect ratio of pro-eutectoid ferrite crystal grains is 3.0 or lower, and the average spacing at the narrowest pearlite lamellar spacing is 0.20 ?m or less.

Abstract: Provided is a so-called Lundell-type generator capable of avoiding generation of eddy current in rotor iron-cores without complicated structure. The generator includes a stator, a rotary shaft, first and second rotor iron-cores, and a rotor coil. Each rotor iron-core includes a base and rotor magnetic-pole portions extending axially from the base, the rotor coil disposed on the inside thereof. Each rotor iron-core is formed of a plurality of unit plates stacked axially. The unit plates integrally include respective basal plate portions stacked to form the bases and a plurality of magnetic-pole plate portions stacked to form the rotor magnetic-pole plate portions stacked to form the rotor magnetic-pole portions.

Abstract: The present invention is a steel for a mechanical structure for cold working, the steel characterized in containing C, Si, Mn, P, S, Al, N, and Cr, the remainder being iron and inevitable impurities; the metal composition having pearlite and pro-eutectoid ferrite; the combined area of the pearlite and pro-eutectoid ferrite being 90% or more of the total composition; the area percentage A of the pro-eutectoid ferrite having the relationship A>Ae, where Ae=(0.8?Ceq)×96.75 (Ceq=[C]+0.1×[Si]+0.06×[Mn]?0.11×[Cr], and “(element names)” indicates the element content (percent in mass); and the mean grain size of the pro-eutectoid ferrite and the ferrite in the pearlite being 15 to 25 ?m.

Abstract: Provided are a steel for a mechanical structure for cold working, and a method for manufacturing the same, whereby softening and variations in hardness can be reduced even when a conventional spheroidizing annealing process is performed. A steel having a predetermined chemical composition, the total area ratio of pearlite and pro-eutectoid ferrite being at least 90 area % with respect to the total metallographic structure of the steel, the area ratio (A) of pro-eutectoid ferrite satisfying the relationship A>Ae with an Ae value expressed by a predetermined relational expression, the average equivalent circular diameter of bcc-Fe crystal grains being 15-35 ?m, and the average of the maximum grain diameter and the second largest grain diameter of the bcc-Fe crystal grains being 50 ?m or less in terms of equivalent circular diameter.

Abstract: Provided is a steel for a mechanical structure for cold working, which contains C, Si, Mn, P, S, Al and N and in which the metal structure includes pearlite and ferrite, the total areal proportion of pearlite and ferrite relative to the overall structure is 90% or higher, the average circle-equivalent diameter of bcc-Fe crystal grains surrounded by large angle grain boundaries is 5-15 ?m, the average aspect ratio of pro-eutectoid ferrite crystal grains is 3.0 or lower, and the average spacing at the narrowest pearlite lamellar spacing is 0.20 ?m or less.

Abstract: A hot-rolled steel sheet having a sheet thickness of 2-10 mm and containing specific amounts of C, Mn, Al, and N with iron and unavoidable impurities. With regard to all grains existing at a position of t/4 in depth, t being sheet thickness, an area ratio of grains having a sheet-plane orientation within 10° from (123) plane is 20% or more, a total area ratio of grains having a crystal direction within 10° from <001> direction and grains having a crystal direction within 10° from <110> direction, in a rolling direction, is 25% or less, and an average grain size of all grains is 3-50 ?m.

Abstract: A hot-rolled steel sheet that: has a sheet thickness of 2-10 mm, contains specific amounts of C, Mn, Al, and N, the remainder being iron and unavoidable impurities, and contains ferrite and pearlite in a specified area ratio, the remainder being bainite. In the hot-rolled steel sheet, a number of grains having an aspect ratio of major axis to minor axis of 3 or less is 60% or more of a number of all grains and an average grain size of the all grains is from 3 to 50 ?m.

Abstract: Provided is a so-called Lundell-type generator capable of avoiding generation of eddy current in rotor iron-cores without complicated structure. The generator includes a stator, a rotary shaft, first and second rotor iron-cores, and a rotor coil. Each rotor iron-core includes a base and rotor magnetic-pole portions extending axially from the base, the rotor coil disposed on the inside thereof. Each rotor iron-core is formed of a plurality of unit plates stacked axially. The unit plates integrally include respective basal plate portions stacked to form the bases and a plurality of magnetic—pole plate portions stacked to form the rotor magnetic-pole plate portions stacked to form the rotor magnetic-pole portions.

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: 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 is a steel for a mechanical structure for cold working, the steel characterized in containing C, Si, Mn, P, S, Al, N, and Cr, the remainder being iron and inevitable impurities; the metal composition having pearlite and pro-eutectoid ferrite; the combined area of the pearlite and pro-eutectoid ferrite being 90% or more of the total composition; the area percentage A of the pro-eutectoid ferrite having the relationship A>Ae, where Ae=(0.8?Ceq)×96.75 (Ceq=[C]+0.1×[Si]+0.06×[Mn]?0.11×[Cr], and “(element names)” indicates the element content (percent in mass); and the mean grain size of the pro-eutectoid ferrite and the ferrite in the pearlite being 15 to 25 ?m.

Abstract: Provided are a steel for a mechanical structure for cold working, and a method for manufacturing the same, whereby softening and variations in hardness can be reduced even when a conventional spheroidizing annealing process is performed. A steel having a predetermined chemical composition, the total area ratio of pearlite and pro-eutectoid ferrite being at least 90 area % with respect to the total metallographic structure of the steel, the area ratio (A) of pro-eutectoid ferrite satisfying the relationship A>Ae with an Ae value expressed by a predetermined relational expression, the average equivalent circular diameter of bcc-Fe crystal grains being 15-35 ?m, and the average of the maximum grain diameter and the second largest grain diameter of the bcc-Fe crystal grains being 50 ?m or less in terms of equivalent circular diameter.

Abstract: A high-strength composition iron powder is prepared by mixing an iron base powder with 0.5 to 3.0 mass % of an Fe—Mn powder having a particle diameter of 45 ?m or less and a Mn content in the range of 60 to 90 mass %, 1.0 to 3.0 mass % of a Cu powder, 0.3 to 1.0 mass % of a graphite powder, and 0.4 to 1.2 mass % of a powder lubricant for die-forming while adjusting the ratio of the amount of Mn contained in the Fe—Mn powder to the amount of the Cu powder in the range of 0.1 to 1. The high-strength composition iron powder is press-formed and sintered at a temperature equal to or higher than the melting point of Cu to produce a high-strength sintered part having a tensile strength of 580 MPa or higher without using expensive alloying elements such as Ni and Mo.

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 high-strength composition iron powder is prepared by mixing an iron base powder with 0.5 to 3.0 mass % of an Fe—Mn powder having a particle diameter of 45 ?m or less and a Mn content in the range of 60 to 90 mass %, 1.0 to 3.0 mass % of a Cu powder, 0.3 to 1.0 mass % of a graphite powder, and 0.4 to 1.2 mass % of a powder lubricant for die-forming while adjusting the ratio of the amount of Mn contained in the Fe—Mn powder to the amount of the Cu powder in the range of 0.1 to 1. The high-strength composition iron powder is press-formed and sintered at a temperature equal to or higher than the melting point of Cu to produce a high-strength sintered part having a tensile strength of 580 MPa or higher without using expensive alloying elements such as Ni and Mo.

Abstract: A machine structure steel superior in chip disposability and mechanical properties which contains sulfide-type inclusions such that those particles of sulfide-type inclusions with major axes not shorter than 5 &mgr;m have an average aspect ratio not larger than 5.2 and which also contains coarse particles of sulfide-type inclusions such that the relation a/b≦0.25 is satisfied, where a denotes the number of particles of sulfide-type inclusions with major axes not shorter than 20 &mgr;m, and b denotes the number of particles of sulfide-type inclusions with major axes not shorter than 5 &mgr;m. The machine structure steel exhibits good chip disposability and mechanical properties despite its freedom from lead.

Abstract: Free machining steel for use in machine structures capable of stably and reliably providing excellent machinability (chip disposability and tool life) and mechanical characteristics (transverse direction toughness) comparable, in a Pb free state, with existent Pb-added steels the machining steel being manufactured so as to contain 0.0005 to 0.02 mass % of Mg and provide a distribution index F1 for the sulfide particles defined by the following equation (1) of 0.4 to 0.65 or a distribution index for the sulfide particles defined by the following equation (2) of 1 to 2.5: F1=X1/(A/n)½  (1), or F2=&sgr;F/X2  (2) as described in the specification.