Provided is a hot press-formed member having excellent crack propagation resistance and ductility. The hot press-formed member includes: a base steel sheet and a zinc or zinc alloy plating layer on at least one surface of the base steel sheet. The base steel sheet contains, by wt %, carbon (C): 0.08-0.30%, silicon (Si): 0.01-2.0%, manganese (Mn): 3.1-8.0%, aluminum (Al): 0.001-0.5%, phosphorus (P): 0.001-0.05%, sulfur (S): 0.0001-0.02%, nitrogen (N): 0.02% or less, and a balance of iron (Fe) and other impurities. The hot press-formed member comprises 1-30 area % of retained austenite as a microstructure, and a Mn(wt %)/Zn(wt %) content ratio in an oxide layer of 0.5-1.2 m in a thickness direction from a surface layer of the plating layer is 0.1 or more.

A rail exhibits a high 0.2% proof stress after shipping, which is effective for improving rolling contact fatigue resistance of the rail, the rail having a chemical composition containing C: 0.70% to 0.85%, Si: 0.1% to 1.5%, Mn: 0.4% to 1.5%, P: 0.035% or less, S: 0.010% or less, and Cr: 0.05% to 1.50%, with the balance being Fe and inevitable impurities, and exhibiting, at least 90 days after a preparation date of a steel material inspection certificate of the rail which describes at least a measurement result of a 0.2% proof stress of a head of the rail, an improvement margin of a 0.2% proof stress of 40 MPa or more, relative to the 0.2% proof stress described in the steel material inspection certificate.

A rail exhibits a high 0.2% proof stress after shipping, which is effective for improving rolling contact fatigue resistance of the rail, the rail having a chemical composition containing C: 0.70% to 0.85%, Si: 0.1% to 1.5%, Mn: 0.4% to 1.5%, P: 0.035% or less, S: 0.010% or less, and Cr: 0.05% to 1.50%, with the balance being Fe and inevitable impurities, and exhibiting, at least 90 days after a preparation date of a steel material inspection certificate of the rail which describes at least a measurement result of a 0.2% proof stress of a head of the rail, an improvement margin of a 0.2% proof stress of 40 MPa or more, relative to the 0.2% proof stress described in the steel material inspection certificate.

A hot rolled steel sheet is provided, which is excellent in collision characteristics, excellent in anisotropy of toughness, and high in strength. The hot rolled steel sheet is characterized by containing, by mass %, C: 0.10% to 0.50%, Si: 0.10% to 3.00%, Mn: 0.5% to 3.0%, P: 0.100% or less, S: 0.010% or less, Al: 1.00% or less, N: 0.010% or less and a balance of Fe and impurities, wherein a metal structure at position of thickness from surface in L-cross-section of the steel sheet comprises prior austenite grains of average value of aspect ratios of 2.0 or less, average grain size of 0.1 m to 3.0 m, and coefficient of variation of a standard deviation of grain size distribution/average grain size of 0.40 or more, and a texture with X-ray diffraction intensity ratio of {001}<110> orientation for random samples of 2.0 or more, and the steel sheet has tensile strength of 1180 MPa or more.

A hot rolled steel sheet is provided, which is excellent in collision characteristics, excellent in anisotropy of toughness, and high in strength. The hot rolled steel sheet is characterized by containing, by mass %, C: 0.10% to 0.50%, Si: 0.10% to 3.00%, Mn: 0.5% to 3.0%, P: 0.100% or less, S: 0.010% or less, Al: 1.00% or less, N: 0.010% or less and a balance of Fe and impurities, wherein a metal structure at position of thickness from surface in L-cross-section of the steel sheet comprises prior austenite grains of average value of aspect ratios of 2.0 or less, average grain size of 0.1 m to 3.0 m, and coefficient of variation of a standard deviation of grain size distribution/average grain size of 0.40 or more, and a texture with X-ray diffraction intensity ratio of {001}<110> orientation for random samples of 2.0 or more, and the steel sheet has tensile strength of 1180 MPa or more.

A high-entropy austenitic stainless steel and a preparation method thereof are provided. The elemental composition of the stainless steels developed by the invention is as follows: Cr: 5-30%; Ni: 5-50%; Ti: 1-15%; Al: 1-15%; the rest are Fe and inevitable impurities; preferably, the composition is Cr: 5-19%; Ni: 5-29%; Ti: 6-15%; Al: 5-15%; the rest element is Fe. By adjusting the atomic ratio of each element, the nano-sized precipitates are generated as much as possible, and the strength is maximized while maintaining a high plasticity. The stainless steels provided by this invention have only five alloying components, a low manufacturing cost, and high-strength and high-plasticity. They can be widely used in many industrial fields such as aviation, aerospace, marine, and nuclear power with broad market prospects.

A high-entropy austenitic stainless steel and a preparation method thereof are provided. The elemental composition of the stainless steels developed by the invention is as follows: Cr: 5-30%; Ni: 5-50%; Ti: 1-15%; Al: 1-15%; the rest are Fe and inevitable impurities; preferably, the composition is Cr: 5-19%; Ni: 5-29%; Ti: 6-15%; Al: 5-15%; the rest element is Fe. By adjusting the atomic ratio of each element, the nano-sized precipitates are generated as much as possible, and the strength is maximized while maintaining a high plasticity. The stainless steels provided by this invention have only five alloying components, a low manufacturing cost, and high-strength and high-plasticity. They can be widely used in many industrial fields such as aviation, aerospace, marine, and nuclear power with broad market prospects.

A cold rolled heat treated steel sheet having a composition with the following elements, expressed in percentage by weight 0.1%Carbon0.5%, 1%Manganese3.4%, 0.5%Silicon2.5%, 0.03%Aluminum1.5%, 0%Sulfur0.003%, 0.002%Phosphorus0.02%, 0%Nitrogen0.01% and can contain one or more of the following optional elements 0.05%Chromium1%, 0.001%Molybdenum0.5%, 0.001%Niobium0.1%, 0.001%Titanium0.1%, 0.01%Copper2%, 0.01%Nickel3%, 0.0001%Calcium0.005%, 0%Vanadium0.1%, 0%Boron0.003%, 0%Cerium0.1%, 0%Magnesium0.010%, 0%Zirconium0.010%, the remainder composition being composed of iron and unavoidable impurities caused by processing, the microstructure of the steel sheet having in area fraction, 10 to 30% Residual Austenite, 50 to 85% Bainite, 1 to 20% Quenched Martensite, and less than 30% Tempered Martensite.

A cold rolled heat treated steel sheet having a composition with the following elements, expressed in percentage by weight 0.1%Carbon0.5%, 1%Manganese3.4%, 0.5%Silicon2.5%, 0.03%Aluminum1.5%, 0%Sulfur0.003%, 0.002%Phosphorus0.02%, 0%Nitrogen0.01% and can contain one or more of the following optional elements 0.05%Chromium1%, 0.001%Molybdenum0.5%, 0.001%Niobium0.1%, 0.001%Titanium0.1%, 0.01%Copper2%, 0.01%Nickel3%, 0.0001%Calcium0.005%, 0%Vanadium0.1%, 0%Boron0.003%, 0%Cerium0.1%, 0%Magnesium0.010%, 0%Zirconium0.010%, the remainder composition being composed of iron and unavoidable impurities caused by processing, the microstructure of the steel sheet having in area fraction, 10 to 30% Residual Austenite, 50 to 85% Bainite, 1 to 20% Quenched Martensite, and less than 30% Tempered Martensite.

The present disclosure relates to a CHQ wire rod that has improved resistance to hydrogen delayed fracture while securing cold forging characteristics by reducing Si content and adding Mo and V, a processed product using the same, and a manufacturing method thereof. In accordance with an aspect of the present disclosure, a CHQ wire rod includes, in percent (%) by weight of the entire composition, C: 0.3 to 0.5%, Si: 0.1 to 0.3%, Mn: 0.5 to 1.0%, at least two or more of Cr: 0.5 to 1.5%, Mo: 0.5 to 1.5%, V: 0.01 to 0.2%, the remainder of iron (Fe) and other inevitable impurities, and the value of the following formula (1) is 3.56 or more.