Process for manufacturing steel sheet having very high strength, ductility and toughness characteristics, and sheet thus produced

US9856548B2 · kind B2 · utility

Assignee

• Arcelormittal France · FR

Inventors

• Sebastien Allain · Norroy-lès-Pont-à-Mousson, FR
• Audrey Couturier · Metz, FR
• Thierry Iung · Jarny, FR
• Christine Colin · Auxerre, FR

Key dates

• Filing date: Feb 14, 2007
• Grant date: Jan 2, 2018
• Expiry date: Oct 23, 2028

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C21D2211/008
• WIPO field: Materials, metallurgy
• WIPO sector: Chemistry

Abstract

The invention relates to a hot-rolled steel sheet having a tensile strength of greater than 1200 MPa, an Re/Rm ratio of less than 0.75 and an elongation at break of greater than 10%, the composition of which contains, the contents being expressed by weight: 0.10%≦C≦0.25%; 1%≦Mn≦3%; Al≧0.015%; Si≦1.985%; Mo≦0.30%; Cr≦1.5%; S≦0.015%; P≦0.1%; Co≦1.5%; B≦0.005%; it being understood that 1%≦Si+Al≦2%; Cr+(3×Mo)≧0.3%, the balance of the composition consisting of iron and inevitable impurities resulting from the smelting, the microstructure of the steel consisting of at least 75% bainite, residual austenite in an amount equal to or greater than 5% and martensite in an amount equal to or greater than 2%.