HARDENED MARTENSITIC STEEL HAVING A LOW OR ZERO CONTENT OF COBALT, PROCESS FOR MANUFACTURING A PART

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Steel characterized in that its composition is, in percentages by weight : - C = 0.20 - 0.30%; - Co = traces - 1%; - Cr = 2 - 5%; - Al = 1 - 2%; - Mo + W/2 = 1 - 4%; - V = traces - 0.3%; - Nb = traces - 0.1%; - B = traces - 30 ppm; - Ni = 11 - 16% with Ni ≥ 7 + 3.5 Al; - Si = traces - 1.0%; - Mn = traces - 2.0%; - Ca = traces - 20 ppm; - rare earths = traces - 100 ppm; - when N < 10 ppm, Ti + Zr/2 = traces - 100 ppm with Ti + Zr/2 < 10 N; - when 10 ppm < N < 20 ppm, Ti + Zr/2 = traces - 150 ppm; - O = traces - 50 ppm; - N = traces - 20 ppm; - S = traces - 20 ppm; - Cu = traces - 1%; - P = traces - 200 ppm, the remainder being iron and inevitable impurities resulting from the smelting. Process for manufacturing a part from this steel, and part thus obtained.