Arcelormittal

David Dussaussois

Christian Allely

Tiago Machado Amorim

Raisa Grigorieva

Matthieu Salib

Clément Philippot

Doriane Serra

Hubert Salmon Legagneur

Sandra Le Guillard

A hot-stamped coated steel part includes a steel substrate and an aluminum alloy coating comprising, proceeding from steel substrate outwards, an interdiffusion layer and an outer layer. The total thickness of the coating eand the thickness of the interdiffusion layer esatisfy the following condition: The hot-stamped coated steel part comprises an undeformed portion having a thickness efrom 0.6 mm to 3.5 mm, and at least one deformed portion. A lineic density of cracks dC in the coating in the undeformed portion is higher than or equal to a minimum lineic density of cracks dC(e) defined as:

Crack-containing hot-stamped coated steel part with excellent spot-weldability and excellent painting adhesion

A hot formed pre-coated steel part includes a steel sheet precoated with a metallic coating and hot formed, the coating including: 2.0 to 24.0% by weight of zinc; 1.1 to 7.0% by weight of silicon; optionally from 0.5 to 3.0% by weight of magnesium when the amount of silicon is between 1.1 and 4.0%, and optionally additional elements chosen from Pb, Ni, Zr or Hf, a content by weight of each additional element being less than 0.3% by weight, a balance being aluminum, unavoidable impurities and residual elements resulting from feeding ingots or from a passage of the steel sheet in a molten bath; and a ratio Al/Zn by weight greater than 2.9, where a microstructure in the steel after said hot forming being martensitic or martensitic-bainitic or made of at least 75% of equiaxed ferrite, 5 to 20% of martensite and bainite in an amount less than or equal to 10%.

Hot formed pre-coated steel part

A pre-coated steel sheet includes a steel sheet precoated with a metallic coating, the coating including: 2.0 to 24.0% by weight of zinc; 1.1 to 7.0% by weight of silicon; optionally from 0.5 to 3.0% by weight of magnesium when the amount of silicon is between 1.1 and 4.0%, and optionally additional elements chosen from Pb, Ni, Zr or Hf, a content by weight of each additional element being less than 0.3% by weight, a balance being aluminum, unavoidable impurities and residual elements resulting from feeding ingots or from a passage of the steel sheet in a molten bath; a ratio Al/Zn by weight greater than 2.9, wherein the coating does not include In and the coating does not include Sn.

Coated steel sheet

The present invention provides a method for the manufacture of a hardened part. The method includes the provision of a steel sheet pre-coated with a metallic coating including from 2.0 to 24.0% by weight of zinc, from 1.1 to 7.0% by weight of silicon, optionally from 1.1 to 8.0% by weight of magnesium when the amount of silicon is between 1.1 and 4.0%, and optionally additional elements chosen from Pb, Ni, Zr, or Hf, the content by weight of each additional element being less than 0.3% by weight, the balance being aluminum and unavoidable impurities and residuals elements, wherein the ratio Al/Zn is above 2.9. The method further includes the cutting of the coated steel sheet to obtain a blank, the thermal treatment of the blank at a temperature between 840 and 950&#xb0; C. to obtain a fully austenitic microstructure in the steel, the transfer of the blank into a press tool, the hot-forming of the blank to obtain a part, the cooling of the part in order to obtain a microstructure in steel being martensitic or martensitic-bainitic or made of at least 75% of equiaxed ferrite, from 5 to 20% of martensite and bainite in amount less than or equal to 10%.

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Homécourt, France

David Dussaussois