The invention relates to austenitic-ferritic stainless steel composition, the composition of which includes: 0.01 wt % ≤ C ≤ 0.10 wt %; 20.0 wt % ≤ Cr ≤ 24.0 wt %; 1.0 wt % ≤ Ni ≤ 3.0 wt %; 0.12 wt % ≤ N ≤ 0.20 wt %; 0.5 wt % ≤ Mn ≤ 2.0 wt %; 1.6 wt % ≤ Cu ≤ 3.0 wt %; 0.05 wt % ≤ Mo ≤ 1.0 wt %; W ≤ 0.15 wt %; 0.05 wt % ≤ Mo +W/2 ≤ 1.0 wt %; 0.2 wt % ≤ Si ≤ 1.5 wt %; Al ≤ 0.05 wt %; V ≤ 0.5 wt %; Nb ≤ 0.5 wt %; Ti ≤ 0.5 wt %; B ≤ 0.003 wt %; Co ≤ 0.5 wt %; REM ≤ 0.1 wt %; Ca ≤ 0.03 wt %; Mg ≤ 0.1 wt %; Se ≤ 0.005 wt %; O ≤ 0.01 wt %; S ≤ 0.030 wt %; and P ≤ 0.040 wt %; the remainder being iron and impurities resulting from production, and the microstructure consisting of austenite and 35 to 65 vol % of ferrite. The composition also satisfies the following relations: 40 ≤ IF ≤ 65, where IF = 10 wt % Cr + 5.1 wt % Mo + 1.4 wt % Mn + 24.3 wt % Si + 35 wt % Nb + 71.5 wt % Ti - 595.4 wt % C - 245.1 wt % N - 9.3 wt % Ni - 3.3 wt % Cu - 99.8 and IRCGCU ≥ 32.0, where IRCGCU = wt % Cr + 3.3 wt % Mo + 2 wt % Cu + 16 wt % N + 2.6 wt % Ni - 0.7 wt % Mn and 0 ≤ IU ≤ 6.0, where IU = 3 wt % Ni + wt % Cu + wt % Mn - 100 wt % C - 25 wt % N - 2(wt % Cr + wt % Si) - 6 wt % Mo + 45. The invention also relates to a method for manufacturing sheets, strips, coils, bars, wires, profile sections, forged parts, and molded parts made of said steel.