The present invention provides steel sheet products having controlled compositions that are subjected to two-step annealing processes to produce sheet products having desirable microstructures and favorable mechanical properties such as high strength and ultra-high formability. Steels processed in accordance with the present invention exhibit combined ultimate tensile strength and total elongation (UTS.Math.TE) properties of greater than 25,000 MPa-%. Steels with these properties fall into the category of Generation 3 advanced high strength steels, and are highly desired by various industries including automobile manufacturers.

An austenitic stainless steel according to the present invention has a chemical composition containing, by mass %: C: 0.01 to 0.15%; Si: 2.0% or less; Mn: 3.0% or less; Cr: 10.0 to 20.0%; Ni: 5.0 to 13.0%; N: 0.01 to 0.30%; Nb: 0 to 0.5%; Ti: 0 to 0.5%; and V: 0 to 0.5%, with the balance: Fe and impurities, wherein an average grain size is 10.0 μm or less, a difference in value of an average lattice constant d.sub.Ave. (={d.sub.γ(111)×I.sub.γ(111)+d.sub.γ(200)×I.sub.γ(200)+d.sub.γ(220)×I.sub.γ(220)+d.sub.γ(311)×I.sub.γ(311)}/{I.sub.γ(111)+I.sub.γ(200)+I.sub.γ(220)+I.sub.γ(311)}) of an austenite phase between a surface portion and a center portion is 0.010 Å or more, and a value of a diffraction peak integrated intensity ratio r (=100×ΣI.sub.γ/ΣI.sub.ALL) at a surface is 95% or more.

A high-strength hot-dip galvanized steel sheet has a hot-dip galvanized layer on a surface of the steel sheet, a specific component composition, and a steel microstructure containing, on an area percentage basis, 0% to 15% of ferrite and upper bainite in total, 80% to 100% of lower bainite and martensite in total, and 0% to 10% of retained austenite, and containing precipitates having a particle size of 100 to 2,000 nm in an amount of 10.sup.9 to 10.sup.12 particles/m.sup.2 in a region extending to a position 100 to 300 μm from the surface layer of the steel sheet, in which the ratio of the average amount of C at a position 5 μm from the surface layer of the steel sheet to the average amount of C at a position 70 μm from the surface layer of the steel sheet in the thickness direction is 0.20 to 0.80.

High strength steel sheet improved in formability, bending load, and bendability is provided. The high strength steel sheet has a center part of sheet thickness and a surface soft part formed at one side or two sides of the center part of sheet thickness, has metal structures of the center part of sheet thickness comprised of, by area ratio, tempered martensite: 85% or more, one or more of ferrite, bainite, pearlite, and retained austenite: total of less than 15%, and as-quenched martensite: less than 5%, has metal structures of the surface soft part comprised of, by area ratio, ferrite: 65% or more, pearlite: 5% or more and less than 20%, one or more of tempered martensite, bainite, and retained austenite: total of less than 10%, and as-quenched martensite: less than 5%, has average distances of pearlite at the surface soft part of 3 μm or more, and has Vickers hardness (Hc) of the center part of sheet thickness and Vickers hardness (Hs) of the surface soft part satisfying 0.50≤Hs/Hc≤0.75.

A process for preparing a high carbon martensitic stainless steel is disclosed. Said process for preparing said high-carbon martensitic stainless steel comprises: providing a steel composition comprising 1.7 to 1.9% by weight C, 17 to 18% by weight Cr, 1.6 to 2.0% by weight Mo, 2.9 to 3.5% by weight V, 0.40 to 0.60% by weight Nb, and Fe as main constituent; melting the steel composition; transferring the molten steel composition to a die casting mold; demolding the steel composition at a temperature in a range of 850 to 950° C. followed by forced air cooling; preparing the steel composition for open die forging; subjecting the steel composition to open die forging, subjecting the steel composition to anti-flaking heat treatment, followed by hardening and tempering to obtain the high carbon martensitic stainless steel.

A hot-pressed member, a steel sheet for hot pressing, and methods for producing the hot-pressed member and the steel sheet for hot pressing. The hot-pressed member includes a steel sheet and a Zn-based alloy coated layer disposed on at least one surface of the steel sheet. The Zn-based alloy coated layer includes a solid solution phase including Zn with the balance being Fe and incidental impurities, an intermetallic compound phase including Fe with the balance being Zn and incidental impurities, and an oxide layer including Zn. The oxide layer serves as an uppermost layer of the Zn-based alloy coated layer and splits the intermetallic compound phase. The split density in at least one cross-section of the oxide layer per unit cross-section is 10 split positions/mm or more.

The invention relates to a method for producing a patterned stainless steel sheet with modified visual characteristics in the wavelength area of visible light the deformed stainless steel having a thickness of 0.3-3.5 mm. In the method the deformed stainless steel sheet is pretreated by at least one heat treatment step and at least one mechanical treatment step on at least one surface of the heat treated stainless steel sheet. The pretreated stainless steel sheet is further transferred to a patterning process, and at least one heat treatment step is carried out on the patterned stainless steel sheet surface.

High-strength galvannealed steel sheet including any of a) an oxide containing Fe and Mn, b) an oxide containing Fe and Mn and an Fe oxide, c) an oxide containing Fe and Mn and a Mn oxide, d) an oxide containing Fe and Mn, an Fe oxide, and a Mn oxide, and e) an Fe oxide and a Mn oxide is present in a zinc coated layer. The total amount of oxide is 0.01 to 0.100 g/m.sup.2; the ratio by mass % of Mn to Fe, e.g., Mn/Fe, contained in the oxide is 0.10 to 10.00; an oxide of at least one selected from Fe and Mn is present in an amount of 60% or more; and an oxide of at least one selected from Fe and Mn is present in a surface layer portion of a steel sheet in an amount of 0.040 g/m.sup.2 or less (not including zero).

A steel sheet, a plated steel sheet, and methods for producing a hot-rolled steel sheet, a cold-rolled full hard steel sheet, and a steel sheet. The steel sheet has a specified composition and a microstructure including 0 to 80% of polygonal ferrite and 20 to 100% of a total of martensite, bainite, and residual austenite in terms of an area ratio within 20 μm of the steel sheet surface. The content of Mn in martensite present within 20 μm of the steel sheet surface ([Mn].sub.SM) and the content of Mn in a bulk ([Mn].sub.B) satisfy [Mn].sub.SM/[Mn].sub.B≤1.5. At a location 300 μm from the steel sheet surface, an area ratio of the martensite is in a range of 20 to 50%.

A method for producing a cold rolled steel sheet having a tensile strength≥1470 MPa and a total elongation TE≥19%, the method comprising the steps of annealing at an annealing temperature AT≥Ac3 a non-treated steel sheet whose chemical composition contains in weight %: 0.34%≤C≤0.40%, 1.50%≤Mn≤2.30%, 1.50≤Si≤2.40%, 0%<Cr≤0.5%, 0%<Mo≤0.3%, 0.01%≤Al≤0.07%, the remainder being Fe and unavoidable impurities, quenching the annealed steel sheet by cooling it to a quenching temperature QT<Ms transformation point and between 150° C. and 250° C., and making a partitioning treatment by reheating the quenched steel sheet to a partitioning temperature PT between 350° C. and 420° C. and maintaining the steel sheet at this temperature during a partitioning time Pt between 15 seconds and 120 seconds.