TEMPERED MARTENSITIC STEEL, METHOD OF PRODUCING A PART FROM SAID STEEL AND PART THUS OBTAINED

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The invention relates to steel which is characterised by the following composition as expressed in percentages by weight : - C = 0.18 0.30 %, - Co = 5 -7 %, - Cr = 2 - 5 %, - Al = 1 - 2 %, - Mo + W/2 = 1 - 4 %, - V = trace 0.3 %, - Nb = trace 0.1 %, - B = trace - 50 ppm, - Ni = 10.5 - 15 % with Ni ≥ 7 + 3.5 Al, - Si = trace 0.4 %, - Mn = trace 0.4 %, - Ca = trace - 500 ppm, - Rare earths = trace - 500 ppm, - Ti = trace - 500 ppm, - O = trace - 200ppm if the steel is obtained by means of powder metallurgy or trace - 50 ppm if the steel is produced in air or under a vacuum from molten metal, - N = trace - 100 ppm, - S = trace - 50 ppm, - Cu = trace - 1 %, and - P = trace - 200 ppm, the remainder comprising iron and the inevitable impurities resulting from production. The invention also relates to a method of producing a part from said steel and to the part thus obtained.