The purpose of one aspect of the present disclosure is to provide: a cold rolled steel sheet for a flux-cored wire, having excellent low temperature toughness, welding workability and processability; and a manufacturing method thereof. One embodiment of the present disclosure provides: a cold rolled steel sheet for a flux-cored wire, comprising, by wt %, 0.005-0.10% of C, 0.05-0.25% of Mn, 0.05% or less of Si (excluding 0%), 0.0005-0.01% of P, 0.008% or less of S (excluding 0%), 0.005-0.06% of Al, 0.0005-0.003% of N, 0.8-1.7% of Ni, 0.1-0.5% of Cr, and a balance of Fe and inevitable impurities, and having 0.10-0.75 of WN defined by Relationship 1 below; and a manufacturing method therefor. Relationship 1: WN=(31C+0.5Mn+20Al)(Ni)(0.6Cr).

Steel wire rod etc. enabling elimination the heat treatment processes of spheroidizing annealing and of quenching and tempering are provided. A predetermined chemical composition is provided, 90% or more of the microstructure by area ratio is bainite, the mean bainite block size of the surface layer measured at the cross-section is 15 m or less, the ratio of the mean bainite block size of the surface layer measured at the cross-section and the mean bainite block size measured at the center part is less than 1.0, and the mean particle size of cementite dispersed in bainite is 0.1 m or less.

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.

A wire rod according to an aspect of the present invention includes a chemical composition within a predetermined range; in which an average value of % Mn+2 x % Cr over an entirety of the wire rod is 0.50% to 1.00%; 90% or more of a metallographic structure is pearlite by area fraction, and the area fraction of the cementite is less than 3%; a maximum grain size of TiN is less than 15 m; a maximum value of % Mn+2 x % Cr in a region where both a S content and an 0 content are less than 1% in a central portion is 2.0 times or less than the average value of % Mn+2x % Cr over the entirety of the wire rod, and a ratio of the maximum value to a minimum value of % Mn+2x % Cr in a region where both a S content and an 0 content are less than 1% in an outer circumferential portion is 2.0 or less.

Provided is a railway wheel capable of suppressing formation of pro-eutectoid cementite even if the C content is high. A railway wheel according to an embodiment of the present invention has a chemical composition consisting of: in mass %, C: 0.80 to 1.15%; Si: 0.45% or less; Mn: 0.10 to 0.85%; P: 0.050% or less; S: 0.030% or less; Al: 0.120 to 0.650%; N: 0.0030 to 0.0200%; Cr: 0 to 0.25%; and V: 0 to 0.12%, with the balance being Fe and impurities, wherein an amount of pro-eutectoid cementite, which is defined by Formula (1), in a microstructure of the railway wheel is not more than 1.50 pieces/100 m:

Amount of pro-eutectoid cementite (pieces/ 100 m)=a total sum of the number of pieces of pro-eutectoid cementite which intersect with two diagonal lines in a square visual field of 200 m200 m/(5.66100 m) (1)

Provided is a low alloy oil-well steel pipe having a yield strength of 827 MPa or more, and an excellent SSC resistance. The low alloy oil-well steel pipe according to the present invention consisting of: in mass %, C: more than 0.35 to 0.65%; Si: 0.05 to 0.50%; Mn: 0.10 to 1.00%; Cr: 0.40 to 1.50%; Mo: 0.50 to 2.00%; V: 0.05 to 0.25%; Nb: 0.01 to 0.040%; sol.Al: 0.005 to 0.10%; N: 0.007% or less; Ti: 0 to 0.012%; Ca: 0 to 0.005%; and a balance being Fe and impurities, the impurities including: P: 0.020% or less; S: 0.002% or less; O: 0.006% or less; Ni: 0.10% or less; Cu: 0.03% or less; and B: 0.0005% or less, wherein in a microstructure, a number of cementite particles each of which has an equivalent circle diameter of 200 nm or more is 200 particles/100 m.sup.2 or more, and a yield strength is 827 MPa or more.

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.

A high strength/highstrength, high toughness steel sheet having tensile strength, Charpy impact absorption energy, and ductile fracture rate are equal to or greater than specified values comprises, in mass %, 0.03-0.08% of C, 0.01-0.50% of Si, 1.5-2.5% of Mn, 0.001-0.010% of P, 0.0030% or less of S, 0.01-0.08% of Al, 0.010-0.080% of Nb, 0.005-0.025% of Ti, 0.001-0.006% of N, at least one substance selected from among 0.01-1.00% of Cu, 0.01-1.00% of Ni, 0.01-1.00% of Cr, 0.01-1.00% of Mo, 0.01-0.10% of V, and 0.0005-0.0030% of B, and a remainder of Fe and unavoidable impurities. At a position at the sheet thickness, the area ratio of island-like martensite is less than 3%, the area ratio of bainite is 90% or more, and the average particle size of cementite within the bainite is 0.5 m or less.

In a track part, in particular rail for railway vehicles, made of a hypereutectoid steel, comprising a rail foot, a rail web and a rail head portion, a hypereutectoid steel with the following directional analysis is used: 0.98-1.17 wt.-% of C 0.90-1.35% wt.-% of Mn 0.70-1.10% wt.-% of Si 0.15-0.70 wt.-% of Cr
and wherein the steel, at least in the head portion of the rail, has a pearlitic structure that is substantially free of secondary cementite networks.

A steel contains, in a chemical composition, C, Si, Mn, and Al, and contains pearlite as a metallographic structure, and a value obtained by dividing an Mn content in a cementite in the pearlite in terms of at % by an Mn content in a ferrite in the pearlite in terms of at % is higher than 0 and equal to or lower than 5.0.