Low-Density Hot-or Cold-Rolled Steel, Method for Implementing Same and Use Thereof

A rolled steel sheet having a density of less than or equal to 7.3 and a composition of which comprises the following elements, expressed in percent by weight:

• 0.10≦C≦0.30%;
• 6.0≦Mn≦15.0%;
• and
• 6.0≦Al≦15.0%,
• the remainder of the composition being composed of iron and the unavoidable impurities caused by processing, wherein
• Mn
• Al
• >
• 1.0
• ,
• and a microstructure of the sheet consists of ferrite, austenite and up to 5% Kappa precipitates in area fraction.

A method for fabricating a rolled steel sheet having a density less than or equal to 7.3, comprising the steps of:

• providing a steel having a composition comprising:
• 0.10≦C≦0.30%;
• 6.0≦Mn≦15.0%;
• and
• 6.0≦Al≦15.0%,
• the remainder of the composition being composed of iron and the unavoidable impurities caused by processing, wherein
• Mn
• Al
• >
• 1.0
• ,
• and a microstructure of the sheet consists of ferrite, austenite and up to 5% Kappa precipitates in area fraction;
• casting the steel to form a semi-finished product;
• rolling the semi-finished product with at least one rolling pass in the presence of ferrite to obtain a sheet, the final rolling temperature TFL being greater than or equal to 850° C.;
• cooling the sheet at a cooling rate Vref1 to a coiling temperature Tbob which is less than or equal to 600° C.;
• and
• coiling the cooled sheet.