Steel sheet with high mechanical strength, ductility and formability properties, production method and use of such sheets

US9427939B2 · kind B2 · utility

Assignee

• ARCELORMITTAL INVESTIGACIÓN Y DESARROLLO, S.L. · ES

Inventors

• Sebastien Allain · Norroy-lès-Pont-à-Mousson, FR
• Jan Mahieu · Dendermonde, BE
• Mickael Denis Crouvizier · Mondelange, FR
• Thierry Mastrorillo · Serémange-Erzange, FR
• Arnaud Hennion · Dalhem, BE

Key dates

• Filing date: May 3, 2012
• Grant date: Aug 30, 2016
• Expiry date: Aug 16, 2033

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y10T428/12799
• WIPO field: Materials, metallurgy
• WIPO sector: Chemistry

Abstract

The present invention provides a cold rolled steel sheet. The steel sheet has a strength greater than 1000 MPa, a uniform elongation greater than 12% and a V-bendability greater than 90°. The composition of the steel sheet includes, expressed in per cent by weight, 0.15%≦C≦0.25%, 1.8%≦Mn≦3.0%, 1.2%≦Si≦2%, 0%≦Al≦0.10%, 0%≦Cr≦0.50%, 0%≦Cu≦1%, 0%≦Ni≦1%, 0%≦S≦0.005%, 0%≦P≦0.020%, Nb≦0.015%, Ti≦0.020%, V≦0.015%, Co≦1%, N≦0.008%, B≦0.001% whereby Mn+Ni+Cu≦3%. The remainder of the composition consists of iron and inevitable impurities resulting from processing. The microstructure includes, in area percentage, 5 to 20% polygonal ferrite, 10 to 15% residual austenite, 5 to 15% martensite and a balance of bainite. The bainite is in the form of laths and includes carbides between the laths. A number N of inter-lath carbides larger than 0.1 micrometers per unit of surface area is less than or equal to 50000/mm2. A fabrication method and a motor vehicle are also provided.