Sidmar N.v.

Arcelormittal France Sa

Arcelormittal France

Sven Vandeputte

Serge Claessens

Christophe Mesplont

Sigrid Jacobs

The present invention is related to a steel composition, a process for producing a steel product having said composition, and said steel product itself. According to the invention, a cold-rolled, possibly hot dip galvanized steel sheet is produced with thicknesses lower than 1 mm, and tensile strengths between 800 MPa and 1600 MPa, while the A80 elongation is between 5 and 17%, depending on the process parameters. The composition is such that these high strength levels may be obtained, while maintaining good formability and optimal coating quality after galvanising. The invention is equally related to a hot rolled product of the same composition, with higher thickness (typically about 2 mm) and excellent coating quality after galvanising.

Ultra high strength steel composition, the process of production of an ultra high strength steel product and the product obtained

The present invention describes an ultra-low carbon bake hardenable galvanized or galvannealed steel product, having a higher yield strength at the temperature of the molten zinc bath while maintaining a low yield strength and excellent bake hardening properties in a skinpassed condition, BH being higher than 35 MPa and BH higher than 40 MPa (GI) and BH >20 MPa and BH >30 MPa (GA), as well as having a superior paint appearance after stamping and painting. The content in the steel composition of the Ti is comprised between 3.42 N and 3.42 N&plus;60 ppm for a fixed nitrogen content (N), and the Nb-content, comprised between 50 ppm and 100 ppm, is fixed so that no substantial precipitation of niobium carbides will occur during the process.

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Ruisbroek, Belgium

Sven Vandeputte