A case hardening steel having excellent fatigue resistance is provided at relatively low production cost. A case hardening steel has a chemical composition containing C: 0.10% to 0.30%, Si: 0.10% to 1.20%, Mn: 0.30% to 1.50%, S: 0.010% to 0.030%, Cr: 0.10% to 1.00%, B: 0.0005% to 0.0050%, Sb: 0.005% to 0.020%, and N: 0.0150% or less in a predetermined range, and further containing Al: 0.010%≤Al≤0.120% in the case where B−(10.8/14)N≥0.0003%, and 27/14[N−(14/10.8)B+0.030]≤Al≤0.120% in the case where B−(10.8/14)N<0.0003%.

A steel composition, a reinforcement part of a vehicle using the steel composition and a method of manufacturing the reinforcement part using the steel composition are provided. In particular, the steel composition includes increased content of carbon components and the steel composition is processed by rapid heating and immediate quenching.

A steel composition, a reinforcement part of a vehicle using the steel composition and a method of manufacturing the reinforcement part using the steel composition are provided. In particular, the steel composition includes increased content of carbon components and the steel composition is processed by rapid heating and immediate quenching.

Method for producing a precoated steel blank including the successive steps of: —providing a precoated steel strip including a steel substrate having, on at least one of its main faces, a precoating, the precoating including an intermetallic alloy layer and a metallic layer extending atop said intermetallic alloy layer, the metallic layer being a layer of aluminum, a layer of aluminum alloy or a layer of aluminum-based alloy, —laser cutting the precoated steel strip in order to obtain at least one precoated steel blank, the precoated steel blank including a laser cut edge surface resulting from the laser cutting operation, the laser cut edge surface including a substrate portion and a precoating portion, wherein the laser cutting is carried out in such a way that the substrate portion of the laser cut edge directly resulting from the cutting operation has an oxygen content greater than or equal to 15% in weight.

The present invention relates to a zinc plated steel sheet having excellent surface quality and spot weldability, and a manufacturing method therefore. A zinc plated steel sheet according to one aspect of the present invention comprises a base steel sheet and a zinc-based plating layer formed on the surface of the base steel sheet, wherein the GDOES profile of oxygen, which is measured in the depth direction from the surface of the base steel sheet, has a form in which a local minimum point and a local maximum point alternately appear in the depth direction from the surface, and the difference (a local maximum value—a local minimum value) between the oxygen concentration (a local minimum value) at the local minimum point and the oxygen concentration (a local maximum value) at the local maximum point can be 0.1 wt % or more.

Disclosed is a follow-up process-omitting type high-strength hot-rolled steel sheet having an excellent yield ratio and a method for manufacturing the same. The hot-rolled steel sheet includes, in percent by weight (wt %), 0.12% or more and less than 0.3% of C, 0.5% or less of Si (excluding 0), 0.1 to 2.5% of Mn, 0.0005 to 0.005% of B, 0.02% or less of P, 0.01% or less of S, and the balance of Fe and inevitable impurities, has a microstructure including at least 95 vol % of martensite, has a yield ratio (yield strength/tensile strength) of 0.75 or more, is manufactured by continuous hot rolling, and is manufactured without performing a follow-up process such as cold rolling and heat treatment.

The present disclosure relates to an aluminum-based plated steel that is provided for vehicles by hot forming, an aluminum-based alloy plated steel manufactured using the same, and method of manufacturing thereof.

The present disclosure relates to an aluminum-based plated steel that is provided for vehicles by hot forming, an aluminum-based alloy plated steel manufactured using the same, and method of manufacturing thereof.

An anti-collapse oil casing with high strength and a manufacturing method therefor, comprising the following chemical elements in percentage by mass: C:0.08%-0.18%; Si:0.1%-0.4%; Mn:0.1%-0.28%; Cr:0.2%-0.8%; Mo:0.2%-0.6%; Nb:0.02%-0.08% b; V:0.01%-0.15%; Ti:0.02%-0.05%; B:0.0015%-0.005%; and Al:0.01%-0.05%. The manufacturing method for the anti-collapse oil casing with high strength comprises the steps of: (1) smelting and continuous casting; (2) perforating, rolling, and sizing; (3) controlled cooling: the initial cooling temperature being Ar3+50° C. and the final cooling temperature being ≤80° C.; the cooling step being performed only to the outer surface of the casing without performing to the inner wall of the casing; and the rate of the controlled cooling being 30-70° C./s; (4) tempering; and (5) thermal straightening. The anti-collapse oil casing with high strength according to the present invention has reasonable chemical composition and process design, which not only has excellent economic efficiency, but also has high strength, high toughness and high anti-collapse performance.

Provided is a steel component with excellent surface fatigue strength. The steel component has a nitride compound layer with a thickness of 5.0 μm to 30.0 μm and a hardened layer in an order from a component surface to a component inside, where a thickness of a porous layer on an outermost surface of the nitride compound layer is 3.0 μm or less and 40.0% or less of a thickness of the nitride compound layer, and the hardened layer has a hardness of HV600 or more at a position of 50 μm inward from the component surface, a hardness of HV400 or more at a position from the component surface to the component inside of 400 μm, and a hardness of HV250 or more at a position from the component surface to the component inside of 600 μm.