A method for producing a cold rolled steel sheet having a tensile strength TS of at least 1470 MPa and a total elongation TE of at least 19%, the mechanical properties being measured in the transverse direction relative to the direction of rolling, the method comprising the successive steps of: - annealing at an annealing temperature AT a cold rolled steel sheet made of steel whose chemical composition contains in weight %: 0.36 % ≤ C ≤ 0.40 % 1.50 % ≤ Mn ≤ 2.30 % 1.50 ≤ Si ≤ 2.40 % 0 % < Cr < 0.05 % 0 % < Mo < 0.05 % 0.01 % ≤ Al ≤ 0.08 % the remainder being Fe and unavoidable impurities, including less than 0.05% Ni, less than 0.05% Cu, less than 0.007% V, less than 0.001% B, less than 0.005% S, less than 0.02% P and less than 0.010% N, the annealing temperature AT being higher than the Ac3 transformation point of the steel and less than 1000°C in order to obtain an annealed steel sheet having a structure completely austenitic, and maintaining the steel sheet between AT-5°C and AT+10°C for a time of more than 30 s, - quenching the annealed steel sheet by cooling it down to a quenching temperature QT lower than the Ms transformation point of the steel and between 190 °C and 210 °C, at a cooling rate fast enough to avoid ferrite formation upon cooling in order to obtain a quenched steel sheet having a structure consisting of martensite and austenite and, - making a partitioning treatment by reheating the quenched steel sheet at a partitioning temperature PT between 350°C and 450°C and maintaining the steel sheet at this temperature during a partitioning time Pt between 90 seconds and 110 seconds - after partitioning the steel sheet is cooled to the room temperature in order to obtain a non-coated steel sheet, having a structure containing at least 60% of martensite and between 12% and 15% of austenite. - annealing at an annealing temperature AT a cold rolled steel sheet made of steel whose chemical composition contains in weight %: 0.36 % ≤ C ≤ 0.40 % 1.50 % ≤ Mn ≤ 2.30 % 1.50 ≤ Si ≤ 2.40 % 0 % < Cr < 0.05 % 0 % < Mo < 0.05 % 0.01 % ≤ Al ≤ 0.08 % the remainder being Fe and unavoidable impurities, including less than 0.05% Ni, less than 0.05% Cu, less than 0.007% V, less than 0.001% B, less than 0.005% S, less than 0.02% P and less than 0.010% N, the annealing temperature AT being higher than the Ac3 transformation point of the steel and less than 1000°C in order to obtain an annealed steel sheet having a structure completely austenitic, and maintaining the steel sheet between AT-5°C and AT+10°C for a time of more than 30 s, 0.36 % ≤ C ≤ 0.40 % 1.50 % ≤ Mn ≤ 2.30 % 1.50 ≤ Si ≤ 2.40 % 0 % < Cr < 0.05 % 0 % < Mo < 0.05 % 0.01 % ≤ Al ≤ 0.08 % - quenching the annealed steel sheet by cooling it down to a quenching temperature QT lower than the Ms transformation point of the steel and between 190 °C and 210 °C, at a cooling rate fast enough to avoid ferrite formation upon cooling in order to obtain a quenched steel sheet having a structure consisting of martensite and austenite and, - making a partitioning treatment by reheating the quenched steel sheet at a partitioning temperature PT between 350°C and 450°C and maintaining the steel sheet at this temperature during a partitioning time Pt between 90 seconds and 110 seconds - after partitioning the steel sheet is cooled to the room temperature in order to obtain a non-coated steel sheet, having a structure containing at least 60% of martensite and between 12% and 15% of austenite.