In a hot stamped steel, when [C] represents an amount of C (mass %), [Si] represents an amount of Si (mass %), and [Mn] represents an amount of Mn (mass %), an expression of 5×[Si]+[Mn])/[C]>10 is satisfied, a metallographic structure includes 80% or more of a martensite in an area fraction, and optionally, further includes one or more of 10% or less of a pearlite in an area fraction, 5% or less of a retained austenite in a volume ratio, 20% or less of a ferrite in an area fraction, and less than 20% of a bainite in an area fraction, TS×λ, which is a product of TS that is a tensile strength and λ that is a hole expansion ratio is 50000 MPa.Math.% or more, and a hardness of the martensite measured with a nanoindenter satisfies H2/H1<1.10 and σHM<20.

A method for manufacturing parts is provided. The method includes cold rolling a substrate with work cylinders whose work surface has a roughness Ra.sub.2.5 of less than or equal to 3.6 μm, depositing the metal coating on at least one face of the annealed substrate by electrodeposition to form the metal sheet and deforming the cut metal sheet to form the parts. The outer surface of the metal coating has a waviness Wa.sub.0.8 of less than or equal to 0.5 μm after the deformation step. A part and vehicle are also provided.

A method for manufacturing parts is provided. The method includes cold rolling a substrate with work cylinders whose work surface has a roughness Ra.sub.2.5 of less than or equal to 3.6 μm, depositing the metal coating on at least one face of the annealed substrate by electrodeposition to form the metal sheet and deforming the cut metal sheet to form the parts. The outer surface of the metal coating has a waviness Wa.sub.0.8 of less than or equal to 0.5 μm after the deformation step. A part and vehicle are also provided.

A coated metal sheet is provided. The coated metal sheet includes a steel substrate, a metal coating on at least one face of the steel substrate, the metal coating comprising at least 40% by weight of zinc; and a layer coating an outer surface of the metal coating, the layer including an amino acid in a neutral or salt form, the amino acid being selected from among alanine, arginine, aspartic acid, cysteine, glutamine, lysine, methionine, proline, serine, threonine, or of a mixture thereof, the amount of said amino acid or of said mixture being from 0.1 to 200 mg/m.sup.2, and optionally a base or a mixture of bases, or an acid or a mixture of acids.

A coated metal sheet is provided. The coated metal sheet includes a steel substrate, a metal coating on at least one face of the steel substrate, the metal coating comprising at least 40% by weight of zinc; and a layer coating an outer surface of the metal coating, the layer including an amino acid in a neutral or salt form, the amino acid being selected from among alanine, arginine, aspartic acid, cysteine, glutamine, lysine, methionine, proline, serine, threonine, or of a mixture thereof, the amount of said amino acid or of said mixture being from 0.1 to 200 mg/m.sup.2, and optionally a base or a mixture of bases, or an acid or a mixture of acids.

High strength galvannealed steel sheet having, a) a composition consisting of (in wt. %): C 0.10-0.2, Mn 2.0-3.0, Si 0.2-0.5, Cr 0.1-0.7, Ti 0.01-0.07, Al≤0.2, Nb<0.05, Mo<0.1, optionally B 0.001-0.005, balance Fe apart from impurities, b) a multiphase microstructure comprising (in vol. %) retained austenite 4-20, martensite 5-25, bainitic ferrite ≤10, polygonal ferrite ≤10, balance bainite+tempered martensite 50-90, c) a tensile strength (Rm) 1180-1300 MPa, a yield strength (R.sub.p0.2) 800-970 MPa, an elongation (A50) ≥8%, or an elongation (A80) ≥6%, and d) a bendability value Ri/t of ≤4 for a sample having the size of 35 mm×100 mm, wherein Ri is the bending radius in mm and t is the thickness in mm of the steel sheet.

High strength galvannealed steel sheet having, a) a composition consisting of (in wt. %): C 0.10-0.2, Mn 2.0-3.0, Si 0.2-0.5, Cr 0.1-0.7, Ti 0.01-0.07, Al≤0.2, Nb<0.05, Mo<0.1, optionally B 0.001-0.005, balance Fe apart from impurities, b) a multiphase microstructure comprising (in vol. %) retained austenite 4-20, martensite 5-25, bainitic ferrite ≤10, polygonal ferrite ≤10, balance bainite+tempered martensite 50-90, c) a tensile strength (Rm) 1180-1300 MPa, a yield strength (R.sub.p0.2) 800-970 MPa, an elongation (A50) ≥8%, or an elongation (A80) ≥6%, and d) a bendability value Ri/t of ≤4 for a sample having the size of 35 mm×100 mm, wherein Ri is the bending radius in mm and t is the thickness in mm of the steel sheet.

The present invention relates to aluminum plated steel sheet which does not require coating after plating and is high in production flexibility enabling application of conventional production processes as they are or exhibits excellent corrosion resistance to flex fuels and further is excellent in appearance and to fuel tanks characterized by being produced using the steel sheet. The Si, Mg, Ca, and Ti ingredients in the aluminum plating layer are defined and the cooling method after hot dip aluminum coating is controlled to make Mg.sub.2Si particles with a long axis of 10 μm or less and an aspect ratio of 1 to 3 finely disperse in the plating layer. Due to the Mg.sub.2Si particles, it is possible to give an excellent corrosion resistance to flex fuels and suppress the deterioration in appearance due to MgO.

The present invention relates to aluminum plated steel sheet which does not require coating after plating and is high in production flexibility enabling application of conventional production processes as they are or exhibits excellent corrosion resistance to flex fuels and further is excellent in appearance and to fuel tanks characterized by being produced using the steel sheet. The Si, Mg, Ca, and Ti ingredients in the aluminum plating layer are defined and the cooling method after hot dip aluminum coating is controlled to make Mg.sub.2Si particles with a long axis of 10 μm or less and an aspect ratio of 1 to 3 finely disperse in the plating layer. Due to the Mg.sub.2Si particles, it is possible to give an excellent corrosion resistance to flex fuels and suppress the deterioration in appearance due to MgO.

Zn alloy plated steel material having excellent weldability and processed-part corrosion resistance and a method for production of Zn alloy plated steel material are provided. In the Zn alloy plated steel material comprising base steel material and a Zn alloy plating layer, the Zn alloy plating layer includes, by wt %, Al: 0.1-5.0%, Mg: 0.1-5.0%, as well as a remainder of Zn and inevitable impurities. The Zn alloy plated steel material includes a lower interface layer and an upper interface layer between the base steel material and the Zn alloy plating layer, wherein the lower interface layer is formed on the base steel material and has a dense structure, and the upper interface layer is formed on the lower interface layer and has a network-type or island-type structure.