Provided are a hot dip galvanized steel sheet comprising a base steel sheet wherein the base steel sheet has a predetermined composition and contains 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%, remaining structures consist of bainite, when defining a region having a hardness of 90% or less of the hardness at a position of ¼ thickness to the base steel sheet side from an interface of the base steel sheet and a hot dip galvanized layer as a “soft layer”, there is a soft layer having a thickness of 10 μm or more at the base steel sheet side from the interface, the soft layer contains tempered martensite, and an increase rate in a thickness direction of an area % of tempered martensite from the interface to the inside of the base steel sheet inside the soft layer is 5.0%/pm or less, and a method for producing the same.

A cryogenic pressure vessel of formed of an ASTM A553 Type 1 cryogenic steel alloy including in wt. %: C: 0.01-0.04; Mn: up to 2.0; P: up to 0.02; S: up to 0.15; Si: up to 1.0; Ni: 7-11; Cr: up to 1.0; Mo: up to 0.75; V: up to 0.2; Nb: up to 0.1; Al: up to 0.1; and N: up to 0.01. The steel alloy may have an ultimate tensile strength of at least 900 MPa, a total elongation of at least 20%; a microstructure including between 5 and 20 area % reverted austenite and the remainder tempered martensite; a transverse Charpy impact energy of at least 27 J at −196° C.; and a lateral expansion of at least 0.381 mm at −196° C.

A high strength steel strip having medium amounts of C, Mn, Si, Cr and Al, wherein the steel strip has a microstructure consisting of, in vol. %: ferrite and bainite together 50-90%, martensite <15%, retained austenite 5-15%, the remainder being pearlite, cementite, precipitates and inclusions together up to 5%.

A steel sheet has a predetermined chemical composition, in which a metallographic structure in a surface layer region ranging from a surface to a position of 20 μm from the surface in a sheet thickness direction consists of ferrite and a secondary phase having a volume fraction of 1.0% to 15.0%, the metallographic structure in an internal region ranging from a position of more than 20 μm from the surface in the sheet thickness direction to a ¼ thickness position from the surface in the sheet thickness direction consists of ferrite and a secondary phase having a volume fraction of 5.0% to 25.0%, the volume fraction of the secondary phase in the surface layer region is less than the volume fraction of the secondary phase in the internal region, and in the surface layer region, the average grain size of the secondary phase is 0.5 μm to 4.0 μm, and a texture in which an X.sub.ODF{001}/{111} as the ratio of the intensity of {001} orientation to an intensity of {111} orientation in the ferrite is 0.70 to 2.50 is included.

Provided is an electric resistance welded steel pipe or tube that develops no quench cracks despite having carbon content of 0.40% or more and has excellent fatigue strength. An electric resistance welded steel pipe or tube comprises: a chemical composition containing, in mass %, C: 0.40% to 0.55%, Si: 0.10% to 1.0%, Mn: 0.10% to 2.0%, P: 0.10% or less, S: 0.010% or less, Al: 0.010% to 0.100%, Cr: 0.05% to 0.30%, Ti: 0.010% to 0.050%, B: 0.0005% to 0.0030%, Ca: 0.0001% to 0.0050%, and N: 0.0005% to 0.0050%, with a balance consisting of Fe and inevitable impurities; and a ferrite decarburized layer at each of an outer surface and an inner surface, the ferrite decarburized layer having a depth of 20 μm to 50 μm from the surface.

The en-bloc heat treatment of a manganese steel product whose alloy has a carbon fraction (C) in the following range 0.02≤C≤0.35% by weight, and a manganese content (Mn) in the following range of 3.5% by weight≤Mn≤6% by weight. The en-bloc annealing method has the following substeps: heating (E1) the steel product to a first holding temperature (T1) which is in the range of 820° C.±20° C., first holding (H1) of the steel product during a first holding period (δ1) at the first holding temperature (T1), faster first cooling (A1) of the steel product to a second holding temperature (T2) which is in the range between 350° C. and 450° C., second holding (H2) of the steel product during a second holding period (δ2) in the range of the second holding temperature (T2), performing a slower second cooling (A2).

Provided are a 1500 MPa-grade steel with a high product of strength and elongation for vehicles and a manufacturing method thereof. The mass percentages of the chemical elements thereof are: 0.1-0.3% of C, 0.1-2.0% of Si, 7.5-12% of Mn, 0.01-2.0% of Al, and the balance of iron and other inevitable impurities. The microstructure of the steel with a high product of strength and elongation for vehicles is austenite+martensite+ferrite or austenite+martensite. The steel for vehicles can reach a grade of 1500 MPa, and has a product of strength and elongation of no less than 30 GPa %.

A method for manufacturing a hot-stamped part includes reheating a steel slab at a temperature of 1,200° C. to 1,250° C., the steel slab including, by wt %, 0.20 to 0.50% carbon (C), 0.05 to 1.00% silicon (Si), 0.10 to 2.50% manganese (Mn), more than 0% and not more than 0.015% phosphorus (P), more than 0% and not more than 0.005% sulfur (S), 0.05 to 1.00% chromium (Cr), 0.001 to 0.009% boron (B), 0.01 to 0.09% titanium (Ti), and a balance of iron (Fe) and inevitable impurities; finish-rolling the reheated steel slab at a temperature of 880° C. to 950° C.; cooling the hot-rolled steel plate without using water, and coiling the cooled steel plate at a temperature of 680° C. to 800° C. to form a hot-rolled decarburized layer on a surface of the steel plate; pickling the coiled steel plate, followed by cold rolling; annealing the cold-rolled steel plate in a reducing atmosphere; plating the annealed steel plate; and hot-stamping the plated steel plate.

The invention relates to a method for producing a sheet steel component by means of a press hardening or form hardening process, the sheet steel component being produced by virtue of the fact that a sheet bar composed of at least one region made of a highly hardenable carbon/manganese/boron steel and at least one dual-phase steel is cold-formed, then heated, and then quenched in a cooling press or a sheet bar composed of at least one region made of a highly hardenable carbon/manganese/boron steel and at least one region made of a dual-phase steel is heated to a temperature above the austenitization temperature of the highly hardenable steel material and is then formed into the sheet steel component in a single stroke or in a plurality of strokes in a forming and cooling press, wherein as a softer material and as a partner for the highly hardenable carbon/manganese/boron steel, a dual-phase steel is used, whose Ac3 value is increased until at the required annealing temperatures, with the austenitization of the carbon/manganese/boron steel, only a partial austenitization of the dual-phase steel takes place so that when loaded into the cooling press, the dual-phase steel has a ferritic matrix, and in addition to this, austenite is present.

A metal sheet component including (in % by weight) C: up to 0.5%, Si: 0.05-1%, Mn: 4-12%, Cr: 0.1-4%, Al: up to 3.5%, N: up to 0.05%, P: up to 0.5%, S: up to 0.01%, Cu, Ni: in total up to 2%, Ti, Nb, V: in total up to 0.5%, rare earth metals: up to 0.1%, and as a remainder, Fe and unavoidable impurities, wherein the content % C of C and the content % Cr of Cr meet the following condition: (10% C)+% Cr<5.5%. In order to manufacture a metal sheet component, a flat steel product is heated to a heating temperature, which is at least 200 C. and at most 800 C., and then formed into the component by hot forming the flat steel product heated to the heating temperature, with the structure of the hot-formed metal sheet component having 5-50% by volume austenite and, as the remainder, martensite, tempered martensite and/or ferrite, wherein the ferrite proportion can also be 0, and the average grain diameter of the structure is less than 5 m.