A steel having enhanced weldability for producing submarine hulls

Abstract

Steel for producing submarine hulls, characterised in that the chemical composition thereof comprises, in % by weight: 0.030% ≤ C < 0.080% 0.040% ≤ Si ≤ 0.48% 0.1 %≤Mn ≤1.4% 2% ≤ Ni ≤ 4% Cr ≤ 0.3% 0.30% ≤Mo + W / 2 + 3 (V + Nb / 2 + Ta / 4) ≤ 0.89% Mo ≥ 0.15% V+Nb / 2 + Ta / 4 ≤ 0.004% Nb ≤ 0.004% Cu ≤ 0.45% Al ≤ 0.1% Ti ≤ 0.04% N ≤ 0.0300% the balance being iron and impurities resulting from the production operation, boron being an impurity whose content is less than 0.0005%, and P + S ≤ 0.015%, the chemical composition complying with the condition: 410 ≤ 540 x C°.25 + 245 [ Mo + W / 2 + 3 (V + Nb / 2 + Ta / 4)]°.30 460. The steel having a substantially martensitic or lower bainitic structure, comprising at least 90% of martensite or lower bainite, a maximum of 5% of residual austenite, a maximum of 5% of ferrite. The steel having a yield strength of between 480 MPa and 620 MPa and a Charpy toughness V, Kcv, greater than 50 J at -60°C.