A bearing part (10) is composed of a steel, and has a quench-hardened layer (11) in a surface of the bearing part. The quench-hardened layer includes a plurality of martensite crystal grains. The plurality of martensite crystal grains are classified into a first group and a second group. A minimum value of crystal grain sizes of the martensite crystal grains belonging to the first group is larger than a maximum value of crystal grain sizes of the martensite crystal grains belonging to the second group. A value obtained by dividing a total area of the martensite crystal grains belonging to the first group by the total area of the plurality of martensite crystal grains is more than or equal to 0.3. A value obtained by dividing, by the total area of the plurality of martensite crystal grains, a total area of the martensite crystal grains belonging to the first group except for a martensite crystal grain that has a minimum crystal grain size and that belongs to the first group is less than 0.3. An average grain size of the martensite crystal grains belonging to the first group is less than or equal to 1.5 m. The quench-hardened layer (11) further includes a plurality of cementite grains. A number density of cementite grains each having a grain size of more than or equal to 1 m is more than or equal to 0.025/m.sup.2.

An oil ring wire (2) containing an alloy steel as a material. The alloy steel contains: 0.50 to 0.65% by mass C; 1.60 to 2.30% by mass Si; 0.60 to 1.10% by mass Mn; 0.75 to 1.15% by mass Cr; 0.18 to 0.45% by mass Ni; 0.05 to 0.15% by mass V; and 0.15% by mass or less Cu. In the oil ring wire 2, an area percentage of a carbide is 1.00% or less. Also disclosed is a method of producing the oil ring wire.

Provided are a QT heat treated high carbon hot rolled steel sheet, a high carbon cold rolled steel sheet, a QT heat treated high carbon cold rolled steel sheet, and manufacturing methods thereof, wherein the QT heat treated high carbon hot rolled steel sheet comprises, in weight %, C: 1.0-1.4%, Si: 0.1-0.4%, Mn: 0.1-0.8%, Cr: 0.3-11%, W: 0.05-2.5%, P: 0.03% or less, S: 0.03% or less, Al: 0.02% or less, and the balance being Fe and other inevitable impurities, the average size of carbides being 0.1-20 m.

A cold-rolled and heat-treated steel sheet, has a composition comprising, by weight percent: n0.10%C0.25%, 3.5%Mn6.0%, 0.5%Si2.0%, 0.3%Al1.2%, with Si+Al0.8%, 0.10%Mo0.50%, S0.010%, P0.020%, N0.008%. The cold-rolled steel sheet has a microstructure consisting of, in surface fraction: between 10% and 45% of ferrite, having an average grain size of at most 1.3 m, the product of the surface fraction of ferrite by the average grain size of the ferrite being of at most 35 m %, between 8% and 30% of retained austenite, the retained austenite having an Mn content higher than 1.1*Mn %, Mn % designating the Mn content of the steel, at most 8% of fresh martensite, at most 2.5% of cementite and partitioned martensite.

A hot dip galvanized steel sheet includes a base steel sheet and a hot dip galvanized layer on at least one surface of the base metal steel sheet, wherein the base steel sheet has a predetermined chemical composition, and contains, by volume fraction, ferrite: 0% to 50%, retained austenite: 0% to 30%, tempered martensite: 5% or more, fresh martensite: 0% to 10%, and pearlite and cementite in total: 0% to 5%, when there are remaining structures, the remaining structures consist of bainite, a concentration of B atoms at prior austenite grain boundaries is 2.0 atm % or more, and an average effective crystal grain size is 7.0 m or less, and a method for producing the same.

A steel sheet with excellent phosphatability, according to one embodiment of the present invention, comprises, by wt %, 0.02-0.06% of carbon (C), 0.01% or less of silicon (Si) (excluding 0%), 0.1-0.24% of manganese (Mn), 0.02% or less of aluminum (Al) (excluding 0%), 0.015-0.04% of phosphorus (P), and the balance of iron (Fe) and inevitable impurities, and has an oxide layer having a thickness of 10 nm or less inward from the surface of the steel sheet, and satisfies the following formula 1.

([Mn]+[Si]+[Al])/(3[P])0.6 [Formula 1]

(In formula 1, [Mn], [Si], [Al] and [P] mean the maximum amount of each element when elemental analysis is carried out in the thickness direction of the oxide layer.)

Disclosed are a high-strength multiphase steel tinned raw plate and a manufacturing method therefor, wherein the mass percentages of the components of the multiphase steel tinned raw plate are: 0.081%-0.14% of C, 0.2%-0.8% of Mn, 0.01%-0.09% of Al, 0.01%-0.03% of P, 0.002%-0.015% of N, also containing one or more than one of 0.001%-0.005% of B, 0.005%-0.05% of Cr, 0.001%-0.1% of Ti, 0.001%-0.2% of Nb, 0.005%-0.03% of Cu, 0.001%-0.008% of Mo, and the balance of Fe and other inevitable impurities; and satisfy: 0.21%?Mn+1.3 Cr+3.2 Mo+0.5 Cu?0.91%. The tinned raw plate has a structure comprising ferrite grains, pearlite, martensite and cementite particles, wherein the total volume fraction of the pearlite, martensite and cementite particles is 5%-20%, the volume fraction of the martensite is 1%-5%, and the martensite has a solid solution content of carbon of ?0.07%. The tinned raw plate has a high strength and better elongation, and can be used to produce a can body, a can bottom, an easy-open end and a twist-off cap, etc. of a three-piece can which has higher requirements for strength and elongation.

The railway wheel according to the present embodiment 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: 0.200 to 1.500%, N: 0.0200% or less, Nb: 0.005 to 0.050%, Cr: 0 to 0.25%, and V: 0 to 0.12%, with the balance being Fe and impurities, wherein at least in the microstructure of the rim part and the web part, the amount of pro-eutectoid cementite defined by Formula (1) is 2.00 pieces/100 m or less:
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)100(1).

A steel sheet with a high concentration of contained Mn having an excellent uniform elongation characteristic and high strength is provided. A steel sheet characterized by containing, by mass %, C: greater than 0.10% and less than 0.55%, Si: 0.001% or more and less than 3.50%, Mn: greater than 4.00% and less than 9.00%, sol. Al: 0.001% or more and less than 3.00%, and a balance of iron and unavoidable impurities, wherein a metal structure at a position of thickness from a surface in an L-cross-section of the steel sheet comprises, by area %, 25% to 90% of tempered martensite, 3% or less of ferrite, 10% to 75% of residual austenite, and 5% or less of bainite.

A steel composition is provided and includes carbon of about 0.5 to 0.7 wt %; silicon of about 1.3 to 2.3 wt %; manganese of about 0.6 to 1.2%; chromium of about 0.6 to 1.2 wt %; molybdenum of about 0.1 to 0.5 wt %; nickel of about 0.05 to 0.8 wt %; vanadium of about 0.05 to 0.5 wt %; niobium of about 0.05 to 0.5 wt %; titanium of about 0.05 to 0.3 wt %; cobalt of about 0.01 to 3 wt %; zirconium of about 0.001 to 0.2 wt %; yttrium of about 0.01 to 1.5 wt %; copper of about 0.3% or less but greater than 0 wt %; aluminum of about 0.3% or less but greater than 0 wt %; nitrogen of about 0.03% or less but greater than 0 wt %; oxygen of about 0.003% or less but greater than 0 wt %. Additionally, a balance iron, based on the total weight is included.