Hardened martensitic steel, method for producing a component from this steel and component obtained in this manner
View Patent ↗The invention relates to steel which is characterized 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−200 ppm 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.
1. Steel, characterised in that the composition thereof is, 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 levels−0.3%
—Nb=trace levels−0.1%
—B=trace levels−50 ppm
—Ni=10.5-15% with Ni≧7+3.5 Al
—Si=trace levels−0.4%
—Mn=trace levels−0.4%
—Ca=trace levels−500 ppm
—Rare earth elements=trace levels−500 ppm
—Ti=trace levels−500 ppm
—O=trace levels−200 ppm if the steel is obtained by means of powder metallurgy, or trace levels−50 ppm if the steel is obtained by means of production in air or under vacuum from liquid metal
—N=trace levels−100 ppm
—S=trace levels−50 ppm
—Cu=trace levels−1%
—P=trace levels−200 ppm
the remainder being iron and inevitable impurities resulting from the production operation,
wherein Rm at ambient temperature is between 2200 and 2350 MPa.
2. Steel according to claim 1 , characterised in that it contains C=0.20-0.25%.
3. Steel according to claim 1 , characterised in that it contains Cr=2-4%.
4. Steel according to claim 1 , characterised in that it contains Al=1-1.6%.
5. Steel according to claim 1 , characterised in that it contains Mo=1-4%.
6. Steel according to claim 1 , characterised in that it contains Mo+W/2=1-2%.
7. Steel according to claim 1 , characterised in that it contains V=0.2-0.3%.
8. Steel according to claim 1 , characterised in that it contains Nb=trace levels−0.05%.
9. Steel according to claim 1 , characterised in that it contains Si=trace levels−0.25%.
10. Steel according to claim 1 , characterised in that it contains Mn=trace levels−0.25%.
11. Steel according to claim 1 , characterised in that it contains Ti=trace levels−100 ppm.
12. Steel according to claim 1 , characterised in that it contains 0=trace levels−10 ppm.
13. Steel according to claim 1 , characterised in that it contains N=trace levels−50 ppm.
14. Steel according to claim 1 , characterised in that it contains S=trace levels−10 ppm.
15. Steel according to claim 1 , characterised in that it contains P=trace levels−100 ppm.
16. Steel according to claim 1 , characterised in that the martensitic conversion temperature Ms thereof is greater than or equal to 140° C., with Ms=550−350×C%−40×Mn%−17×Cr%−10×Mo%−17×Ni%−8×W%−35×V%−10×Cu%−10×Co%+30×Al%° C.
17. Steel according to claim 1 , characterised in that it contains Al=1.4-1.6%.
18. Steel according to claim 1 , characterised in that it contains Si=trace levels−0.10%.
19. Steel according to claim 1 , characterised in that it contains Mn=trace levels−0.10%.
20. Steel according to claim 1 , characterised in that it contains N=trace levels−10 ppm.
21. Steel according to claim 1 , characterised in that it contains S=trace levels−5 ppm.
22. Steel according to claim 1 , characterised in that it contains Cr=3.29-5%.
23. Steel according to claim 1 , wherein Rm is about 1800 MPa at 400° C.