MARTENSITIC STAINLESS STEEL AND METHOD FOR PRODUCING SAME

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A martensitic stainless steel, characterized in that its composition is, in percentages by weight : 0.005% ≤ C ≤ 0.30%; 0.20% ≤ Mn ≤ 2.0%; traces % ≤ Si ≤ 1.0%; 0.20% ≤ Mn + Si ≤ 1.5%; traces ≤ S ≤ 0.01%; 0 ≤ 10, 000 x Mn x S ≤ 40; traces ≤ P ≤ 0.04%; 10.5% ≤ Cr ≤ 17.0%, with [Cr - 10.3 - 80 x (C + N)2] ≤ (Mn + Ni); traces ≤ Ni ≤ 4.0%; traces ≤ Mo ≤ 2.0%; traces ≤ Mo + 2W ≤ 2.0%; traces ≤ Cu ≤ 2.0%; traces ≤ Ti ≤ 0.5%; traces ≤ V ≤ 0.3%; traces ≤ Zr ≤ 0.5%; traces ≤ Al ≤ 0.2%; traces ≤ O ≤ 400 ppm; traces ≤ Ta ≤ 0.3%; traces ≤ Nb ≤ 0.3%; 0.25 ≤ (Nb + Ta)/(C + N) ≤ 8; Nb ≥ [1.2 (C + N) - 0.1]%; 0.009% ≤ N ≤ 0.2%; traces ≤ Co ≤ 2.0%; traces ≤ Cu + Co ≤ 2.0%; traces ≤ Cu + Co + Ni ≤ 4.0%; traces ≤ B ≤ 0.1%; traces ≤ rare earth + Y ≤ 0.06%; traces ≤ Ca ≤ 20 ppm; the remainder being iron and impurities resulting from production; and in that its microstructure contains at least 75% martensite, at most 20% ferrite and at most 0.5% carbides, the size of the ferrite grains being between 4 and 80 μm, preferably between 5 and 40 μm. Method for producing said steel.