Abstract: A low density hot rolled steel including of 0.12%?carbon?0.25%, 3%?manganese?10%, 3.5%?aluminum?6.5%, 0%?phosphorus?0.1%, 0%?sulfur?0.03%, 0%?nitrogen?0.1%, 0%?silicon?2%, 0.01%?niobium?0.03%, 0.01%?titanium?0.2%, 0%?molybdenum?0.5%, 0%?chromium?0.6%, 0.01%?copper?2.0%, 0.01%?nickel?3.0%, 0%?calcium?0.005%, 0%?boron?0.01%, 0%?Magnesium?0.005%, 0%?Zirconium?0.005%, 0%?Cerium?0.1%, and the balance including iron and unavoidable impurities, the steel sheet having a microstructure including of ferrite from 60% to 80%, 10% to 35% kappa carbides (Fe,Mn)3AICx, where x is lower than or equal to 1 and austenite from 0% to 10% wherein the microstructure grains having less than 4 GPa nano-hardness must be more than 45% and microstructure grains having nano-hardness of more than 5 GPa must be less than 10%.

Abstract: A method for producing a heat treated cold rolled steel sheet having a composition comprising of the following elements, 0.1%?Carbon?0.25%, 2.15%?Manganese?3.0%, 1%?Silicon?0.8%, 0.1%?Aluminum?0.9%, 0.05%?Chromium?0.5%, 0%?Phosphorus?0.09%, 0%?Sulfur?0.09%, 0%?Nitrogen?0.09%, 2.4%?C+Mn?3%, 0%?Niobium?0.1%, 0%?Titanium?0.1%, 0%?Vanadium?0.1%, 0%?Molybdenum?1%, 0%?Nickel?1%, 0%?Calcium?0.005%, 0%?Boron?0.01%, 0%?Cerium?0.1%, 0%?Magnesium?0.05%, 0%?Zirconium?0.05% the remainder being composed of iron and unavoidable impurities, the method including hot rolling, cooling the hot rolled steel at a cooling rate of at least 30° C./s to a coiling temperature less than 600° C.; and coiling, cooling to room temperature, cold rolling, annealing the cold rolled steel sheet using a two step heating process, cooling, overaging, and cooling to room temperature.

Abstract: A heat treated cold rolled steel sheet having a composition comprising of the following elements, 0.1%?Carbon?0.25%, 2.15%?Manganese?3.0%, 1%?Silicon?0.8%, 0.1%?Aluminum?0.9%, 0.05%?Chromium?0.5%, 0%?Phosphorus?0.09%, 0%?Sulfur?0.09%, 0%?Nitrogen?0.09%, 2.4%?C+Mn?3%, 0%?Niobium?0.1%, 0%?Titanium?0.1%, 0%?Vanadium?0.1%, 0%?Molybdenum?1%, 0%?Nickel?1%, 0%?Calcium?0.005%, 0%?Boron?0.01%, 0%?Cerium?0.1%, 0%?Magnesium?0.05%, 0%? Zirconium?0.05% the remainder being composed of iron and unavoidable impurities, the microstructure of said steel sheet including, 20% to 70% Martensite, 5 to 60% of Inter-critical Ferrite, 5 to 30% of Transformed Ferrite, 8% to 20% of Residual Austenite and 1 to 20% Bainite, wherein the cumulated amount of Inter-critical and Transformed Ferrite is between 15% and 65%.

Abstract: A low density hot rolled steel including of 0.12%?carbon?0.25%, 3%?manganese?10%, 3.5%?aluminum?6.5%, 0%?phosphorus?0.1%, 0%?sulfur?0.03%, 0%?nitrogen?0.1%, 0%?silicon?2%, 0.01%?niobium?0.03%, 0.01%?titanium?0.2%, 0%?molybdenum?0.5%, 0%?chromium?0.6%, 0.01%?copper?2.0%, 0.01%? nickel?3.0%, 0%?calcium?0.005%, 0%?boron?0.01%, 0%?Magnesium?0.005%, 0%?Zirconium?0.005%, 0%?Cerium?0.1%, and the balance including iron and unavoidable impurities, the steel sheet having a microstructure including of ferrite from 55% to 80%, 15% to 50% austenite and martensite from 0% to 10% wherein the microstructure grains having less than 4 GPa nano-hardness must be more than 45% and microstructure grains having nano-hardness of more than 5 GPa must be less than 22%.

Abstract: A low density hot rolled steel including of 0.12%?carbon?0.25%, 3%?manganese?10%, 3.5%?aluminum?6.5%, 0%?phosphorus?0.1%, 0%?sulfur?0.03%, 0%?nitrogen?0.1%, 0%?silicon?2%, 0.01%?niobium?0.03%, 0.01%?titanium?0.2%, 0%?molybdenum?0.5%, 0%?chromium?0.6%, 0.01%?copper?2.0%, 0.01%?nickel?3.0%, 0%?calcium?0.005%, 0%?boron?0.01%, 0%?Magnesium?0.005%, 0%?Zirconium?0.005%, 0%?Cerium?0.1%, and the balance including iron and unavoidable impurities, the steel sheet having a microstructure including of ferrite from 60% to 80%, 10% to 35% kappa carbides (Fe,Mn)3AlCx, where x is lower than or equal to 1 and austenite from 0% to 10% wherein the microstructure grains having less than 4 GPa nano-hardness must be more than 45% and microstructure grains having nano-hardness of more than 5 GPa must be less than 10%.

Abstract: A low density cold rolled and annealed steel sheet having 0.12%?carbon?0.25%, 3%?manganese?10%, 3.5%?aluminum?6.5%, 0%?phosphorus?0.1%, 0%?sulfur?0.03%, 0%?nitrogen?0.1%, 0%?silicon?2%, 0.01%?niobium?0.03%, 0.01%?titanium?0.2%, 0%?molybdenum?0.5%, 0%?chromium?0.6%, 0.01%?copper?2.0%, 0.01%?nickel?3.0%, 0%?calcium?0.005%, 0%?boron?0.01%, 0%?Magnesium?0.005%, 0%?Zirconium?0.005%, 0%?Cerium?0.1%, and the balance including iron, the steel sheet having a microstructure comprising 60% to 90% Delta ferrite, 8% to 30% of residual austenite having average grain size between 0.6 and 2 microns, 1.0% to 10% of alpha-ferrite having average grain size between 0.6 and 2 microns and 0% to 2% of kappa precipitates (Fe,Mn)3AlCx, where x is strictly lower than 1.

Abstract: A heat treated cold rolled steel sheet having a composition comprising of the following elements, 0.1%?Carbon?0.25, 2.15%?Manganese?3.0%, 1%?Silicon?0.8%, 0.1%?Aluminum?0.9%, 0.05%?Chromium?0.5%, 0%?, Phosphorus?0.09%, 0%?Sulfur?0.09%, 0%?Nitrogen?0.09%, 2.4%?C+Mn?3%, 0%?Niobium?0.1%, 0% ?Titanium?0.1%, 0%?Vanadium?0.1%, 0%?Molybdenum?1%, 0%?Nickel?1%, 0%?Calcium?0.005%, 0%?Boron?0.01%, 0%?Cerium?0.1%, 0%?Magnesium?0.05%, 0%?Zirconium?0.05% the remainder being composed of iron and unavoidable impurities, the microstructure of said steel sheet including, 20% to 70% Martensite, 5 to 60% of Inter-critical Ferrite, 5 to 30% of Transformed Ferrite, 8% to 20% of Residual Austenite and 1 to 20% Bainite, wherein the cumulated amount of Inter-critical and Transformed Ferrite is between 15% and 65%.

Abstract: A cold rolled and coated steel sheet having a composition including of the following elements, 0.12%?Carbon?0.2%, 1.7%?Manganese?2.10%, 0.1%?Silicon?0.5%, 0.1%?Aluminum?0.8%, 0.1%?Chromium?0.5%, 0%?Phosphorus?0.09%, 0%?Sulfur?0.09%, 0%?Nitrogen?0.09%, Nickel?3%, Niobium?0.1%, Titanium?0.1%, Calcium?0.005%, Copper?2%, Molybdenum?0.5%, Vanadium?0.1%, Boron?0.003%, Cerium?0.1%, Magnesium?0.010%, Zirconium?0.010% the remainder composition being composed of iron and unavoidable impurities caused by processing, the microstructure of the steel sheet including in area fraction, 10 to 60% Bainite, 25 to 55% Ferrite, 5% to 15% Residual Austenite wherein carbon content in residual austenite is between 0.7% and 1% and 5% to 18% Martensite, wherein the cumulated amount of Bainite and Ferrite is at least 70%.