Austenitic, low-density, high-strength steel strip or sheet having a high ductility, method for producing said steel and use thereof

An austenitic, low-density, high-strength steel strip or sheet having a high ductility, comprising in wt. %:

• 0.65-0.9% C;
• 0-0.5% Si;
• 5.0-20.0% Mn;
• 5.5-11.0% Al;
• 0.001-0.05% N;
• 0.02% or less P;
• 0.02% or less S;
• optionally one or more of:
• 0.001-0.01% Ca;
• 0-0.5% V;
• 0.01-0.2% Ti;
• 0-0.2% Nb;
• 0-5.0% Cr;
• 0-0.2% Zr;
• 0-2.0% Cu;
• 0-0.0050% B;
• 0-1.0% Mo;
• 0-0.2% Sb;
• the balance Fe with unavoidable impurities, having a microstructure comprising 70 to 100 area % of austenite, 30 to 0 area % of ferrite, and 0 to 5 area % of a κ-(Fe,Mn)3AlC-carbide phase,
• the strip or sheet having a yield ratio YS/UTS of at least 0.60, and a ratio of Mn/Si>40,
• the steel strip or sheet having a density of less than 7.3 g/cm3, a tensile strength of at least 750 MPa and an elongation at a gauge (length of 50 mm mm) of at least 25%.