Abstract: Provided are a bolt that exhibits excellent delayed fracture resistance at a high strength level of from 1,200 MPa to less than 1,600 MPa in tensile strength, where the possibility of delayed fracture is generally quite high, and a steel material for a bolt to be used as the material for such a bolt. The bolt has a composition satisfying Formulae (1) and (2), and a tensile strength of from 1,200 MPa to less than 1,600 MPa. In Formula (1) and Formula (2), Mo and V represent the contents (% by mass) of Mo and V contained in the steel for a bolt, respectively. 0.48?Mo/1.4+V<1.10 ??(1) 0.8<Mo/V<3.

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: A high-strength steel member having a predetermined chemical composition, having a tensile strength of 1,000 MPa or higher, containing 0.10% or more of, in terms of percent (%) by area, at least one Ti precipitate that has an average size of from 30 to 200 nm in terms of an average equivalent circle diameter and is selected from the group consisting of a Ti carbide, a Ti nitride, and a composite compound thereof, at a location of 1 mm in depth from a surface of the steel member, and containing 0.5 ppm by mass or more of non-diffusible hydrogen that is released in a temperature range of from 400 to 800° C. in a thermal desorption hydrogen analysis.

Abstract: Provided is a steel wire rod for wire drawing containing, in terms of % by mass, C: from 0.90 to 1.20%, Si: from 0.10 to 1.30%, Mn: from 0.20 to 1.00%, Cr: from 0.20 to 1.30%, Al: from 0.005 to 0.050%, and the balance being composed of Fe and impurities, wherein a content of each N, P, and S, which are contained as the impurities, is N: from 0.0070% or less, P: from 0.030% or less, S: from 0.010% or less, and the steel wire rod having a metallographic structure of which 95% or more by volume ratio is a lamellar pearlite structure, wherein the lamellar pearlite structure has an average lamellar spacing of from 50 to 75 nm, an average length of cementites in the lamellar pearlite structure is 1.0 to 4.0 ?m, and a percentage of a number of cementites having a length of 0.5 ?m or less among the cementites in the lamellar pearlite structure is 20% or less.

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: A steel wire includes, as a chemical composition, by mass %, C: 0.40% to 1.10%, Si: 0.005% to 0.350%, Mn: 0.05% to 0.90%, Cr: 0% to 0.70%, Al: 0% to 0.070%, Ti: 0% to 0.050%, V: 0% to 0.10%, Nb: 0% to 0.050%, Mo: 0% to 0.20%, B: 0% to 0.0030%, and a remainder including Fe and impurities; in which a metallographic structure in a cross section includes 80 area % or more of a pearlite structure having a lamellar cementite; an average lamellar spacing which is a spacing between lamellar cementites is 28 nm to 80 nm; an average length of the lamellar cementite is 22.0 ?m or less; among the pearlite structure, a pearlite structure having the lamellar cementite of which an inclination with respect to a longitudinal direction of the steel wire is 15° or less is 40 area % or more; an integration degree of a {110} plane of a ferrite with respect to the longitudinal direction is in a range of 2.0 to 8.0, and a diameter of the steel wire is 1.4 mm or more.

Abstract: A wire rod according to an aspect of the present invention has a predetermined chemical composition, a solute N is 0.0015% or less, a structure in an area from a surface of the wire rod to a depth of ¼ of a diameter of the wire rod in a cross section thereof includes 90.0 area % or more of pearlite, and 0 to 10.0 area % in total of bainite and ferrite, a total amount of martensite and cementite in the area from the surface of the wire rod to the depth of ¼ of the diameter of the wire rod is limited to 2.0 area % or less, and the calculated maximum size of TiN-type inclusions in a surface layer area of the wire rod is 50 ?m or less.

Abstract: Provided is a steel wire rod for wire drawing containing, in terms of % by mass, C: from 0.90 to 1.20%, Si: from 0.10 to 1.30%, Mn: from 0.20 to 1.00%, Cr: from 0.20 to 1.30%, Al: from 0.005 to 0.050%, and the balance being composed of Fe and impurities, wherein a content of each N, P, and S, which are contained as the impurities, is N: from 0.0070% or less, P: from 0.030% or less, S: from 0.010% or less, and the steel wire rod having a metallographic structure of which 95% or more by volume ratio is a lamellar pearlite structure, wherein the lamellar pearlite structure has an average lamellar spacing of from 50 to 75 nm, an average length of cementites in the lamellar pearlite structure is 1.0 to 4.0 ?m, and a percentage of a number of cementites having a length of 0.5 ?m or less among the cementites in the lamellar pearlite structure is 20% or less.

Abstract: A wire rod according to an aspect of the present invention has a predetermined chemical composition, a solute N is 0.0015% or less, a structure in an area from a surface of the wire rod to a depth of ¼ of a diameter of the wire rod in a cross section thereof includes 90.0 area % or more of pearlite, and 0 to 10.0 area % in total of bainite and ferrite, a total amount of martensite and cementite in the area from the surface of the wire rod to the depth of ¼ of the diameter of the wire rod is limited to 2.0 area % or less, and the calculated maximum size of TiN-type inclusions in a surface layer area of the wire rod is 50 ?m or less.

Abstract: A wire rod according to the present invention includes a predetermined chemical composition, wherein a metal structure includes 90 area % to 100 area % of bainite, wherein when eight test pieces having a length of 400 mm, which are obtained by dividing a wire rod having a length of 3200 mm into eight components having a same length, are manufactured, an average tensile strength TS of each test pieces satisfies a relation of “[TS]?810×[C]+475” by N/mm2, wherein a difference between a maximum value and a minimum value of the tensile strengths of each test pieces is 50 N/mm2 or less, and wherein an average reduction of area RA of each test pieces satisfies a relation of “[RA]??0.083×[TS]+154” by %.

Abstract: A steel wire rod which is a material of steel wires includes, as a metallographic structure, by area %, 95% to 100% of a pearlite, wherein an average pearlite block size at a central portion of the steel wire rod is 1 ?m to 25 ?m, an average pearlite block size at a surface layer portion of the steel wire rod is 1 ?m to 20 ?m, and, when a minimum lamellar spacing of the pearlite at the central portion of the steel wire rod is S in unit of nm and when a distance from a peripheral surface of the steel wire rod to a center is r in unit of mm, S<12r+65 is satisfied.

Abstract: The present invention provides a wire rod with a composition at least including: C: 0.95-1.30 mass %; Si: 0.1-1.5 mass %; Mn: 0.1-1.0 mass %; Al: 0-0.1 mass %; Ti: 0-0.1 mass %; P: 0-0.02 mass %; S: 0-0.02 mass %; N: 10-50 ppm; O: 10-40 ppm; and a balance including Fe and inevitable impurities, wherein 97% or more of an area in a cross-section perpendicular to the longitudinal direction of the wire rod is occupied by a pearlite, and 0.5% or less of an area in a central area in the cross-section and 0.5% or less of an area in a first surface layer area in the cross-section are occupied by a pro-eutectoid cementite.

Abstract: A torsion beam is configured in an arch shape and comprised of an open cross-section member including an arch lower-half portion and an arch upper-half portion. A sectional shape of the arch lower-half portion in a cross section perpendicular to a longitudinal direction of the arch lower-half portion is configured to be substantially horizontal when a vehicle is in a standard state, and a central portion, in the vehicle width direction, of the torsion beam is configured such that a front edge portion of the arch lower-half portion and a front edge portion of the arch upper-half portion are located substantially at the same position in a vehicle longitudinal direction when the vehicle is in a full-rebound state. Thereby, the rigidity and the productivity can be endured, attaining low floor-level of the vehicle.

Abstract: A torsion beam is configured in an arch shape and comprised of an open cross-section member including an arch lower-half portion and an arch upper-half portion. A sectional shape of the arch lower-half portion in a cross section perpendicular to a longitudinal direction of the arch lower-half portion is configured to be substantially horizontal when a vehicle is in a standard state, and a central portion, in the vehicle width direction, of the torsion beam is configured such that a front edge portion of the arch lower-half portion and a front edge portion of the arch upper-half portion are located substantially at the same position in a vehicle longitudinal direction when the vehicle is in a full-rebound state. Thereby, the rigidity and the productivity can be endured, attaining low floor-level of the vehicle.

Abstract: A steel wire rod which is a material of steel wires includes, as a metallographic structure, by area %, 95% to 100% of a pearlite, wherein an average pearlite block size at a central portion of the steel wire rod is 1 ?m to 25 ?m, an average pearlite block size at a surface layer portion of the steel wire rod is 1 ?m to 20 ?m, and, when a minimum lamellar spacing of the pearlite at the central portion of the steel wire rod is S in unit of nm and when a distance from a peripheral surface of the steel wire rod to a center is r in unit of mm, S<12 r+65 is satisfied.

Abstract: The present invention provides a wire rod with a composition at least including: C: 0.95-1.30 mass %; Si: 0.1-1.5 mass %; Mn: 0.1-1.0 mass %; Al: 0-0.1 mass %; Ti: 0-0.1 mass %; P: 0-0.02 mass %; S: 0-0.02 mass %; N: 10-50 ppm; O: 10-40 ppm; and a balance including Fe and inevitable impurities, wherein 97% or more of an area in a cross-section perpendicular to the longitudinal direction of the wire rod is occupied by a pearlite, and 0.5% or less of an area in a central area in the cross-section and 0.5% or less of an area in a first surface layer area in the cross-section are occupied by a pro-eutectoid cementite.

Abstract: The present invention provides a wire rod with a composition at least including: C: 0.95-1.30 mass %; Si: 0.1-1.5 mass %; Mn: 0.1-1.0 mass %; Al: 0-0.1 mass %; Ti: 0-0.1 mass %; P: 0-0.02 mass %; S: 0-0.02 mass %; N: 10-50 ppm; O: 10-40 ppm; and a balance including Fe and inevitable impurities, wherein 97% or more of an area in a cross-section perpendicular to the longitudinal direction of the wire rod is occupied by a pearlite, and 0.5% or less of an area in a central area in the cross-section and 0.5% or less of an area in a first surface layer area in the cross-section are occupied by a pro-eutectoid cementite.

Abstract: A plated steel wire for PWS with excellent twist properties contains, in terms of mass %, 0.8 to 1.1% of C, 0.8 to 1.3% of Si, 0.3 to 0.8% of Mn, 0.001 to 0.006% of N, and 0.0004 to 0.0060% of B, where a quantity of solid-solubilized B is at least 0.0002%, also contains either one or both of 0.005 to 0.1% of Al and 0.005 to 0.1% of Ti, and contains as the remainder, Fe and unavoidable impurities, wherein an area fraction of non-pearlite structures in a region from a surface layer down to a depth of 50 ?m is not more than 10%, an area fraction of non-pearlite structures within an entire cross-section is not more than 5%, and a surface of the steel wire is galvanized with a plating quantity within a range from 300 to 500 g/m2.

Abstract: The present invention provides a wire rod with a composition at least including: C: 0.95-1.30 mass %; Si: 0.1-1.5 mass %; Mn: 0.1-1.0 mass %; Al: 0-0.1 mass %; Ti: 0-0.1 mass %; P: 0-0.02 mass %; S: 0-0.02 mass %; N: 10-50 ppm; O: 10-40 ppm; and a balance including Fe and inevitable impurities, wherein 97% or more of an area in a cross-section perpendicular to the longitudinal direction of the wire rod is occupied by a pearlite, and 0.5% or less of an area in a central area in the cross-section and 0.5% or less of an area in a first surface layer area in the cross-section are occupied by a pro-eutectoid cementite.

Abstract: A plated steel wire for a parallel wire strand (PWS) with excellent twist properties can include, in terms of mass %, about 0.8 to 1.1% of C, about 0.8 to 1.3% of Si, about 0.3 to 0.8% of Mn, about 0.001 to 0.006% of N, and about 0.0004 to 0.0060% of B, where a quantity of solid-solubilized B is at least 0.0002%. Such exemplary wire can include either one or both of about 0.005 to 0.1% of Al and/or about 0.005 to 0.1% of Ti, and may contain, as the remainder, Fe and unavoidable impurities. For example, an area fraction of non-pearlite structures in a region from a surface layer down to a depth of about 50 ?m is likely not more than about 10%, an area fraction of non-pearlite structures within an entire cross-section is likely not more than about 5%, and a surface of the steel wire can be galvanized with a plating quantity within a range from about 300 to 500 g/m2.