Disclosed are a low-cost austenitic stainless steel having high strength and high formability and a method for manufacturing same. The low-cost austenitic stainless steel having high strength and high formability according to an embodiment includes, greater than 0% and at most 0.08% of C, 0.2 to 0.25% of N, 0.8 to 1.5% of Si, 8.0 to 9.5% of Mn, 15.0 to 16.5% of Cr, greater than 0% and at most 1.0% of Ni, 0.8 to 1.8% of Cu, and the remainder of Fe and other unavoidable impurities and satisfies Expressions (1) to (4) below.

Ni+0.47Mn+15N≥7.5  (1)

23(C+N)+1.3 Si+0.24(Cr+Ni+Cu)+0.1Mn≥12  (2)

551−462(C+N)−9.2Si−8.1Mn−13.7Cr−29(Ni+Cu)≤70  (3)

11≤1+45C−5Si+0.09Mn+2.2Ni−0.28Cr−0.67Cu+88.6N≤17  (4)

Here, C, N, Si, Mn, Cr, Ni, and Cu represent contents (wt %) of the elements, respectively.

Disclosed are a ferritic stainless steel having improved corrosion resistance and a method for manufacturing same. The ferritic stainless steel according to an embodiment of the present disclosure includes, in percent by weight (wt%), 0.001 to 0.05% of C, 0.001 to 0.05% of N, 0.1 to 1.0% of Si, 0.1 to 1.0% of Mn, 12.0 to 22.0% of Cr, 0.01 to 1.0% of Ti, and 0.01 to 1.0% of Nb, with the balance being Fe and inevitable impurities, wherein an area ratio of microdefects is 2% or less, and a sulfur (S) content in a surface film within 5 mm from the surface is 10% or less.

A ferritic stainless steel sheet is provided that has a chemical composition consisting of, in mass %, C: 0.001 to 0.020%, Si: 0.02 to 1.50%, Mn: 0.02 to 1.50%, P: 0.01 to 0.05%, S: 0.0001 to 0.01%, Cr: 10.0 to 25.0%, Ti: 0.01 to 0.30%, N: 0.001 to 0.030%, and optional elements, with the balance being Fe and unavoidable impurities, wherein: a grain size number is 6 or more; the ferritic stainless steel sheet satisfies the formulas [A+B≥12.0/t], [X+Y≥12.0/(t−0.3)] and [(X+Y)−(A+B)≤5.0] with respect to crystal orientation intensities of a ferrite phase obtained by X-ray diffraction; and the sheet thickness is 1.0 mm or more.

After low-temperature finish rolling has been performed on a steel material having a certain chemical composition, cooling is performed at an average cooling rate of 10° C./s or higher to a temperature of 500° C., rapid cooling is further performed in a temperature range from a Ms temperature to a temperature of (Ms temperature - 200° C.), coiling is thereafter performed in a low temperature range of 250° C. or lower, and the coiled steel sheet is uncoiled and further subjected to rolling with a certain amount or more of rolling load per unit width and the like. Consequently, it is possible to obtain a high-strength hot-rolled steel sheet having a microstructure including, in terms of area fraction, 95% or more of a martensite phase at a position located at ¼ of the thickness of the steel sheet, in which an average aspect ratio of prior austenite grains is 3.0 or more.

A flat steel product for production of a sheet metal component by hot forming includes a steel substrate consisting of a steel including 0.1-3% by weight of Mn and optionally up to 0.01% by weight of B, an aluminium-based coating disposed on at least one side of the steel substrate. A coating here has an applied layer weight of 15-30 g/m.sup.2. In addition, the coating has an Al base layer consisting of 1.0-15% by weight of Si, optionally 2-4% by weight of Fe, 0.1-5.0% by weight of alkali metals or alkaline earth metals, and optional further constituents, the contents of which are limited to a total of not more than 2.0% by weight, and aluminium as the balance.

Disclosed is a cold-rolled and annealed dual-phase steel having a tensile strength of greater than 780 MPa. A matrix structure thereof is fine and uniform martensite+ferrite. The cold-rolled and annealed dual-phase steel contains the following chemical elements in the following mass percentages: C: 0.1%-0.13%, Si: 0.4%-0.8%, Mn: 1.65%-1.9%, Al: 0.01%-0.05%, Nb: 0.01-0.03%, and Ti: 0.01-0.03%. Furthermore, the cold-rolled annealed dual-phase steel does not contain the elements Cr or Mo. In addition, also disclosed is a method for manufacturing the cold-rolled and annealed dual-phase steel, comprising smelting and continuous casting, hot rolling, cold rolling, annealing, tempering and flattening. The cold-rolled and annealed dual-phase steel of the present invention is not only economical, but also has the characteristics of high strength, excellent elongation and cold bending properties.

Provided is a steel sheet having a predetermined chemical composition and microstructure, wherein a block size in a first depth region of 1 to 10 μm from the surface is 5.0 μm or less, a block size in a second depth region of 10 to 60 μm from the surface is 6.0 to 20.0 μm, and a block size in a third depth region of 60 μm to 1/4 thickness from the surface is less than 6.0 μm. Further, provided is a method for producing a steel sheet comprising a step of hot rolling a steel slab having a predetermined chemical composition, then coiling it at 500° C. or more, a step of pickling the hot rolled steel sheet to remove oxide scale, wherein an amount of removal of the surface layer of the hot rolled steel sheet is less than 5.00 μm, a step of cold rolling by a rolling reduction of 30 to 90%, and an annealing step of holding in an atmosphere of a dew point of −20 to 20° C. at a temperature region of 740 to 900° C. for 40 to 300 seconds.

A process for reducing flatness deviations in an alloy article is disclosed. An alloy article may be heated to a first temperature at least as great as a martensitic transformation start temperature of the alloy. A mechanical force may be applied to the alloy article at the first temperature. The mechanical force may tend to inhibit flatness deviations of a surface of the alloy article. The alloy article may be cooled to a second temperature no greater than a martensitic transformation finish temperature of the alloy. The mechanical force may be maintained on the alloy article during at least a portion of the cooling of the alloy article from the first temperature to the second temperature.

The hot-rolled coated steel sheet comprising: in wt %, C: 0.05-0.14%, Si: 0.1-1.0%, Mn: 1.0-2.0%, P: 0.001-0.05%, S: 0.001-0.01%, AI: 0.01-0.1%, Cr: 0.005-1.0%, Ti: 0.005-0.13%, Nb: 0.005-0.03%, N: 0.001-0.01%, Fe residues, and other inevitable impurities; a mixed structure of ferrite and bainite as a main phase; and as a remaining structure, one or more selected from the group consisting of martensite, austenite, and phase martensite (MA), wherein a fraction of the ferrite and bainite is 95-99 area % and Equation 1 is satisfied. [Equation 1] FCO.sub.{110}<112>+FCO.sub.{112}<111>≥10 where, FCO.sub.{110}<112> and FCO.sub.{112}<111>, each representing an area fraction occupied by a structure having ac crystal orientation of {110}<112> and {112}<111>.

The invention relates to a method for producing a flat steel product made of a medium manganese steel having a TRIP/TWIP effect. The aim of the invention is to achieve an improvement in the yield strength when a sufficient residual deformability of the produced flat steel product is obtained. This aim is achieved by the following steps: cold rolling a hot or cold strip, annealing the cold-rolled hot or cold strip at 500 to 840° C. for 1 minute to 24 hours, temper rolling or finishing the annealed hot or cold strip to form a flat steel product having a degree of deformability between 0.3% and 60%. The invention further relates to a flat steel product produced according to said method and to a use thereof.