Abstract: The steel material includes a chemical composition containing, in mass %, C: 0.15 to 0.45%, Si: 0.50% or less, Mn: 0.20 to 0.60%, P: 0.015% or less, S: 0.005% or less, Cr: 0.80 to 1.50%, Mo: 0.17 to 0.30%, V: 0.24 to 0.40%, Al: 0.005 to 0.100%, N: 0.0300% or less, O: 0.0015% or less, and the balance being Fe and impurities, and satisfying Formula (1) to Formula (4) described in Embodiment, wherein, in its microstructure, a total area fraction of ferrite and pearlite is 10.0% or more, and a proportion of a content of V (mass %) in electrolytic extraction residue to the content of V (mass %) in the chemical composition is 10.0% or less.

Abstract: A rolling sliding member includes a base part and a surface layer. The base part has a composition that includes 0.30 mass % to 0.45 mass % of carbon, 0.15 mass % to 0.45 mass % of silicon, 0.40 to 1.50 mass % of manganese, 0.60 mass % to 2.00 mass % of chromium, 0.10 mass % to 0.35 mass % of molybdenum, 0.20 mass % to 0.40 mass % of vanadium, and 0.005 mass % to 0.100 mass % of aluminum, and a remainder of iron and inevitable impurities. The surface layer is positioned around the base part. The surface layer has a Vickers hardness of 700 to 800 and a retained austenite content of 25 volume % to 50 volume %. The thickness of a grain boundary oxide layer satisfies Formula: thickness of grain boundary oxide layer?equivalent diameter of rolling sliding member×1.4×10?3.

Abstract: The steel material includes a chemical composition containing, in mass %, C: 0.15 to 0.45%, Si: 0.50% or less, Mn: 0.20 to 0.60%, P: 0.015% or less, S: 0.005% or less, Cr: 0.80 to 1.50%, Mo: 0.17 to 0.30%, V: 0.24 to 0.40%, Al: 0.005 to 0.100%, N: 0.0300% or less, O: 0.0015% or less, and the balance being Fe and impurities, and satisfying Formula (1) to Formula (4) described in Embodiment, wherein, in its microstructure, a total area fraction of ferrite and pearlite is 10.0% or more, and a proportion of a content of V (mass %) in electrolytic extraction residue to the content of V (mass %) in the chemical composition is 10.0% or less.

Abstract: A core portion of the carbonitrided bearing component includes a chemical composition consisting of, in mass %, C: 0.15 to 0.45%, Si: 0.50% or less, Mn: 0.20 to 0.60%, P: 0.015% or less, S: 0.005% or less, Cr 0.80 to 1.50%, Mo: 0.17 to 0.30%, V: 0.24 to 0.40%, Al: 0.005 to 0.100%, N: 0.0300% or less, O: 0.0015% or less, and the balance being Fe and impurities, and satisfying Formula (1) to Formula (4) described in the embodiment of the present specification. A concentration of C of its surface is, in mass %, 0.70 to 1.20%, a concentration of N of the surface is, in mass %, 0.15 to 0.60%, a Rockwell C-scale hardness HRC of the surface is 58 to 65, and in the core portion, an area ratio of an area of coarse V-based precipitates to a total area of V-based precipitates is 15.0% or less.

Abstract: The steel material for a carburized bearing part according to the present invention contains, by mass %, C: 0.25 to 0.45%, Si: 0.15 to 0.45%, Mn: 0.40 to 1.50%, P: 0.015% or less, S: 0.005% or less, Cr: 0.60 to 2.00%, Mo: 0.10 to 0.35%, V: 0.20 to 0.40%, Al: 0.005 to 0.100%, Ca: 0.0002 to 0.0010%, N: 0.0300% or less and O: 0.0015% or less, with the balance being Fe and impurities, and satisfies Formulae (1) to (3). 1.20<0.4Cr+0.4Mo+4.5V<2.75??(1) A1/A2>0.50??(2) 2.7C+0.4Si+Mn+0.45Ni+0.8Cr+Mo+V>2.55??(3) Formula (2) shows an area fraction of sulfides containing Ca in an amount of 1 mol % or more among sulfides having an equivalent circular diameter of 1 ?m or more.

Abstract: A drawn steel wire has a predetermined chemical composition; in a region of the drawn steel wire that is closer to an axis line than a depth of 100 ?m from a surface of the drawn steel wire in a lengthwise-section that includes the axis line of the drawn steel wire, a metallographic structure includes 90% or more of a drawn pearlite by an area ratio; in a region of the drawn steel wire that is the depth of 100 ?m from the surface of the drawn steel wire in the lengthwise-section, the metallographic structure includes 70% or more of the drawn pearlite by the area ratio; when D in units of millimeters represents a diameter of the drawn steel wire, ?HV represents a standard deviation of a Vickers hardness of the surface of the drawn steel wire, and Rp0.2 represents a yield strength of the drawn steel wire, ?HV<(?9500×ln(D)+30000) exp(?0.003×Rp0.2) is satisfied, and a tensile strength TS of the drawn steel wire is 1770 MPa or higher.

Abstract: This invention provides a high-strength PC steel wire having a chemical composition containing, in mass %, C: 0.90 to 1.10%, Si: 0.80 to 1.50%, Mn: 0.30 to 0.70%, P: 0.030% or less, S: 0.030% or less, Al: 0.010 to 0.070%, N: 0.0010 to 0.010%, Cr: 0 to 0.50%, V: 0 to 0.10%, B: 0 to 0.005%, Ni: 0 to 1.0%, Cu: 0 to 0.50%, and the balance: Fe and impurities. A ratio between the Vickers hardness (HvS) at a location (surface layer) that is 0.1D [D: diameter of steel wire] from the surface of the steel wire and the Vickers hardness (HvI) of a region on the inner side relative to the surface layer satisfies the formula [1.10<HvS/HvI?1.15]. An average carbon concentration in a region from the surface to a depth of 10 ?m (outermost layer region) of the steel wire is 0.8 times or less a carbon concentration of the steel wire. The steel micro-structure in the region on the inner side relative to the outermost layer region contains, in area %, a pearlite structure: 95% or more.

Abstract: This invention provides a high-strength PC steel wire having a chemical composition containing, in mass %, C: 0.90 to 1.10%, Si: 0.80 to 1.50%, Mn: 0.30 to 0.70%, P: 0.030% or less, S: 0.030% or less, Al: 0.010 to 0.070%, N: 0.0010 to 0.010%, Cr: 0 to 0.50%, V: 0 to 0.10%, B: 0 to 0.005%, Ni: 0 to 1.0%, Cu: 0 to 0.50%, and the balance: Fe and impurities. A ratio between the Vickers hardness (HvS) at a location (surface layer) that is 0.1D [D: diameter of steel wire] from the surface of the steel wire and the Vickers hardness (HvI) of a region on the inner side relative to the surface layer satisfies the formula [1.10<HvS/HvI?1.15]. The steel micro-structure in the region from the surface of the steel wire to 0.01D (outermost layer region) consists of, in area %, a pearlite structure: less than 80%, and the balance: a ferrite structure and/or a bainitic structure.

Abstract: The steel material for a carburized bearing part according to the present invention contains, by mass %, C: 0.25 to 0.45%, Si: 0.15 to 0.45%, Mn: 0.40 to 1.50%, P: 0.015% or less, S: 0.005% or less, Cr: 0.60 to 2.00%, Mo: 0.10 to 0.35%, V: 0.20 to 0.40%, Al: 0.005 to 0.100%, Ca: 0.0002 to 0.0010%, N: 0.0300% or less and O: 0.0015% or less, with the balance being Fe and impurities, and satisfies Formulae (1) to (3). 1.20<0.4Cr+0.4Mo+4.5V<2.75??(1) A1/A2>0.50??(2) 2.7C+0.4Si+Mn+0.45Ni+0.8Cr+Mo+V>2.55??(3) Formula (2) shows an area fraction of sulfides containing Ca in an amount of 1 mol % or more among sulfides having an equivalent circular diameter of 1 ?m or more.

Abstract: Steel improved in all of the hardenability, toughness, surface-originated micropitting life, and bending fatigue strength and a part manufactured using such steel are provided having predetermined constituents having an Fn1 defined by the following formula (1) of 0.20 to 0.65 and having an Fn2 defined by the following formula (2) of 0.50 to 1.00: Fn1=4.2×[Cr]/(7.0×[Si]+16.0×[Mn])??(1) [Element]: mass % of element Fn2=A1/A2??(2) A1: total area (?m2) of sulfide-based inclusions containing 1.0 mol % or more of Ca with respect to the total number of moles in the sulfides and having a circle equivalent diameter of 1.0 ?m or more in observation regions of a total area of 4.0 mm2 A2: total area (?m2) of sulfide-based inclusions having a circle equivalent diameter of 1.0 ?m or more in observation regions of a total area of 4.

Abstract: A steel wire rod according to an aspect of the present invention has a chemical composition in a predetermined range, in which a structure in a central part includes 80 area % to 100 area % of pearlite and a total of 0 area % or more and less than 20 area % of proeutectoid ferrite, proeutectoid cementite, martensite, and bainite; an average lamellar spacing of the pearlite in the central part is 50 nm to 100 nm; an average length of lamellar cementite in the central part is 1.9 ?m or less; an average pearlite block size in the central part is 15.0 ?m to 30.0 ?m; a structure in a surface part includes 70 area % to 100 area % of the pearlite; and an average pearlite block size in the surface part is 0.40 times or more and 0.87 times or less the average pearlite block size in the central part.

Abstract: Provided is a high-carbon steel wire rod with excellent wire drawability, containing predetermined chemical components and the balance: Fe and impurities. In a cross-section perpendicular to a longitudinal direction, an area fraction of pearlite is equal to or more than 95% and equal to or less than 100%, an average block size of the pearlite is 10 ?m to 30 ?m and standard deviation of block size is 20 ?m or less, and when Ceq.=C (%)+Si (%)/24+Mn (%)/6, a tensile strength is equal to or more than 760×Ceq.+255 MPa and equal to or less than 760×Ceq.+325 MPa, reduction of area in a tensile test is ?65×Ceq.+96(%) or more, and standard deviation of the reduction of area is 6% or less.

Abstract: A steel wire for a non heat-treated mechanical part includes, as a chemical composition, by mass %, a predetermined amount of C, Si, Mn, Cr, Mo, Ti, Al, B, Nb, and V, and limited P, S, N, and O and a remainder of Fe and impurities; in which a structure includes, by volume %, a bainite of greater than or equal to 75×[C %]+25, and a remainder of one or more of a ferrite and a pearlite when an amount of C is set to [C %] by mass %; when an average aspect ratio of a bainite block in a second surface layer area of the steel wire is set as R1, the R1 is greater than or equal to 1.2; when an average grain size of a bainite block in a third surface layer area of the steel wire is set to PS3 ?m, and an average grain size of a bainite block in a third center portion of the steel wire is set to PC3 ?m, the PS3 satisfies Expression (c), and the PS3 and the PC3 satisfy Expression (d), a standard deviation of a grain size of the bainite block in the structure is less than or equal to 8.

Abstract: A wire rod for a steel cord has a wire diameter R of 3.5 mm to 8.0 mm, and includes, in a chemical composition, by mass %: C: 0.70% to 1.20%; Si: 0.15% to 0.60%; Mn: 0.10% to 1.00%; N: 0.0010% to 0.0050%; Al: more than 0% and 0.0100% or less; and a remainder of Fe and impurities, in which a surface part and a central part are included, a thickness of the surface part is 50 ?m to 0.20×R, the central part includes a pearlite structure in a proportion of 95% to 100% by area %, a C content of the surface part is 40% to 95% of a C content of the central part, and a ratio of a thickness of a lamellar cementite at a center of the thickness of the surface part to a thickness of a lamellar cementite in the central part is 95% or less, whereby high strength and workability can be achieved even after a finish drawing process and cracking or the like caused by a delamination phenomenon can be prevented.

Abstract: A rolling sliding member includes a base part and a surface layer. The base part has a composition that includes 0.30 mass % to 0.45 mass % of carbon, 0.15 mass % to 0.45 mass % of silicon, 0.40 to 1.50 mass % of manganese, 0.60 mass % to 2.00 mass % of chromium, 0.10 mass % to 0.35 mass % of molybdenum, 0.20 mass % to 0.40 mass % of vanadium, and 0.005 mass % to 0.100 mass % of aluminum, and a remainder of iron and inevitable impurities. The surface layer is positioned around the base part. The surface layer has a Vickers hardness of 700 to 800 and a retained austenite content of 25 volume % to 50 volume %. The thickness of a grain boundary oxide layer satisfies Formula: thickness of grain boundary oxide layer?equivalent diameter of rolling sliding member×1.4×10?3.

Abstract: A steel wire for non-heat treated machine parts, the steel wire contains, based on % by mass: C: from 0.20 to 0.40%, Si: from 0.05 to 0.50%, Mn: from 0.50 to 2.00%, Al: from 0.005 to 0.050%, and the balance being Fe and impurities, in which the microstructure contains bainite of (35×[C %]+50)% or more, and when the diameter is defined as D, the average aspect ratio of a bainite grain at a depth of 50 ?m in the L cross section is defined as AR, and the average grain size of a bainite grain at a depth of 50 ?M in the C cross section is defined as GD, AR is 1.4 or more, (AR)/(the average aspect ratio of a bainite grain at a depth of 0.25D in the L cross section) is 1.1 or more, GD is (15/AR) ?m or less, and (GD)/(the average grain size of a bainite grain at a depth of 0.25D in the C cross section) is less than 1.0.

Abstract: A steel wire rod includes required amounts of chemical components and a remainder including Fe and impurities; in which the area ratio of pearlite in a cross section perpendicular to a longitudinal direction is 95% or more and a remainder includes a non-pearlite structure which includes one or more of a bainite, a degenerate pearlite, a proeutectoid ferrite and a proeutectoid cementite; the average block size of the pearlite is 15 ?m to 35 ?m and the area ratio of the pearlite having a block size of 50 ?m or more is 20% or less; and the area ratio of a region where a lamellar spacing of the pearlite is 150 nm or less is 20% or less in a region within a depth from a surface of the steel wire rod of 1 mm or less.

Abstract: A filament for a high strength steel cord has a wire diameter R of 0.1 mm to 0.4 mm, and includes, in a chemical composition, by mass %: C: 0.70% to 1.20%; Si: 0.15% to 0.60%; Mn: 0.10% to 1.00%; N: 0.0010% to 0.0050%; Al: more than 0% and 0.0100% or less; and a remainder of Fe and impurities, in which a surface part and a central part are included, a thickness of the surface part is 0.01×R to 0.10×R, the central part includes a pearlite structure in a proportion of 95% to 100% by area %, a C content of the surface part is 40% to 95% of a C content of the central part, and a ratio of a thickness of a lamellar cementite at a center of the thickness of the surface part to a thickness of a lamellar cementite in the central part is 95% or less, whereby high strength and workability can be achieved and cracking or the like caused by a delamination phenomenon can be prevented.

Abstract: A steel wire according to an aspect of the present invention includes a predetermined chemical composition, in which a wire diameter R of the steel wire is 1.0 mm to 3.5 mm, a soft portion is formed along an outer circumference of the steel wire, the Vickers hardness of the soft portion is lower than that of a position of the steel wire at a depth of ¼ of the wire diameter R by Hv 30 or higher, the thickness of the soft portion is 5 ?m to 0.1×R mm, the metallographic structure of a center portion of the steel wire contains 95% to 100% of pearlite by area %, the average lamellar spacing of pearlite in a portion from a surface of the steel wire to a depth of 5 ?m is less than that of pearlite at the center of the steel wire, the difference between the average lamellar spacing of pearlite in the portion from the surface of the steel wire to the depth of 5 ?m and the average lamellar spacing of pearlite at the center of the steel wire is 3 nm to 60 nm, and the tensile strength is 1100 MPa or higher.

Abstract: A filament according to an aspect of the present invention includes a predetermined chemical composition, in which a diameter r of the filament is 0.15 mm to 0.35 mm, a soft portion is formed along an outer circumference of the filament, the Vickers hardness of the soft portion is lower than that of a position of the filament at a depth of ¼ of the diameter r by Hv 50 or higher, the thickness of the soft portion is 1 ?m to 0.1×r mm, the metallographic structure of a center portion of the filament contains 95% to 100% of pearlite by area %, the average lamellar spacing of pearlite in a portion from a surface of the filament to a depth of 1 ?m is less than that of pearlite at the center of the filament, the difference between the average lamellar spacing of pearlite in the portion from the surface of the filament to the depth of 1 ?m and the average lamellar spacing of pearlite at the center of the filament is 2.0 nm or less, and the tensile strength is 3200 MPa or higher.