The invention relates to sheet steel, more particularly a coated sheet steel, which is skin-pass rolled with a deterministic surface structure, and to a method for producing this steel.

A method operates a continuous annealing line for the processing of a rolled good, in particular a metal strip. A property of the rolled good in relation to a point or a section of the rolled good is fed to a computer-aided model as an input variable. The point or the section of the rolled good is located before or in the continuous annealing line. For the purpose of precise control of the continuous annealing process, at least one material property of the rolled good after the continuous annealing process is simulated by the computer-aided model and compared with a specified target value. If the simulated material property deviates from the target value, at least one process variable of the continuous annealing process is controlled as long as the point or the section of the rolled good is located before or in the continuous annealing line.

The present invention pertains to a hot press forming member having excellent resistance to hydrogen embrittlement, and a method for manufacturing same. An aspect of the present invention provides a hot press forming member having excellent resistance to hydrogen embrittlement, the hot press forming member comprising a base steel plate and an alloy-plated layer formed on the surface of the base steel plate, wherein the alloy-plated layer contains pores such that pores having a size of 5 μm or less constitute 3-30% of the surface area of the alloy-plated layer as viewed in a cross-section taken in the thickness direction of the member.

A galvannealed steel sheet includes: a steel sheet; a coating layer on a surface of the steel sheet; and a mixed layer formed between the steel sheet and the coating layer, in which the mixed layer includes a base iron portion having fine grains having a size of greater than 0 μm and equal to or smaller than 2 μm, a Zn—Fe alloy phase, and oxides containing one or more types of Mn, Si, Al, and Cr, and in the mixed layer, the oxides and the Zn—Fe alloy phase are present in grain boundaries that form the fine grains and the Zn—Fe alloy phase is tangled with the base iron portion.
[Mn]+[Si]+[Al]+[Cr]≧0.4  (Expression 1)

A high-strength high-ductility steel sheet has a specific component composition and a steel microstructure containing, in terms of an area ratio relative to the entire microstructure, 8% or more of a retained austenite, with the remainder being at least one of bainite, martensite, tempered bainite, and tempered martensite. With respect to the carbon concentration in the retained austenite, an average carbon concentration is from 0.9 to 1.2 mass %, a standard deviation of the carbon concentration distribution is 0.35 mass % or more, and an area ratio of a region having the carbon concentration of 1.5 mass % or more, relative to the entire microstructure, is 1.0% or more.

The invention relates to a method for producing an anti-corrosion coating for hardenable sheet steels, wherein at least two metal layers are deposited one after another onto the steel substrate; the one metal layer is a zinc layer or zinc-based layer and the other layer is a layer composed of a metal that forms baser intermetallic phases with Zn or Fe and has a higher oxidation potential than Zn, namely Ni, Cu, Co, Mn, or Mo, or a layer based on these metals; and an anti-corrosion coating for hardenable sheet steels.

A steel sheet suitable as a starting material for a vehicle impact absorbing member with high absorption of impact energy and resistance to cracking contains, by mass %, C: 0.08-0.30%, Mn: 1.5-3.5%; Si+Al: 0.50-3.0%, P: 0.10% or less, S: at most 0.010%, and N: at most 0.010%, and optionally, one or more types selected from Cr: at most 0.5%, Mo: at most 0.5% , B: at most 0.010%, Ti: less than 0.04%, Nb: less than 0.030%, V: less than 0.5%, Ca: at most 0.010%, Mg: at most 0.010%, REM: at most 0.050%, and Bi: at most 0.050%. The microstructure contains, by area %, bainite: more than 50%, martensite: 3-30%, and retained austenite: 3-15%, the remainder comprising ferrite having an average grain diameter of less than 5 mm. The product of uniform elongation and hole expansion ratio is at least 300%.sup.2 and 5% effective flow stress is at least 900 MPa.

A nitrided packaging steel in the form of a flat steel product and method for producing a nitrided packaging steel with a carbon content of 10-1000 ppm and uncombined nitrogen, dissolved in the steel, of more than 100 ppm. The nitriding is performed in two stages: a first stage, in which a molten steel is nitrided to a nitrogen content of at most 160 ppm by introducing a nitrogen-containing gas and/or a nitrogen-containing solid into the molten steel, and a second stage, in which a flat steel product produced from the nitrided molten steel by cold rolling is treated with a nitrogen-containing gas in order to increase further the amount of uncombined nitrogen in the flat steel product. The second stage is performed in an annealing furnace, in which the flat steel product is at the same time annealed in a recrystallizing manner. The packaging steels produced are distinguished by great strength, in excess of 600 MPa, and good elongation to fracture, regularly in excess of 5%, as well as by good forming properties.

A nitrided packaging steel in the form of a flat steel product and method for producing a nitrided packaging steel with a carbon content of 10-1000 ppm and uncombined nitrogen, dissolved in the steel, of more than 100 ppm. The nitriding is performed in two stages: a first stage, in which a molten steel is nitrided to a nitrogen content of at most 160 ppm by introducing a nitrogen-containing gas and/or a nitrogen-containing solid into the molten steel, and a second stage, in which a flat steel product produced from the nitrided molten steel by cold rolling is treated with a nitrogen-containing gas in order to increase further the amount of uncombined nitrogen in the flat steel product. The second stage is performed in an annealing furnace, in which the flat steel product is at the same time annealed in a recrystallizing manner. The packaging steels produced are distinguished by great strength, in excess of 600 MPa, and good elongation to fracture, regularly in excess of 5%, as well as by good forming properties.

Provided is a steel sheet that can be used for automobile parts or the like, and relates to a steel sheet having an excellent balance of strength and ductility, and excellent workability, and a method for manufacturing same.