Alloy for Mud Motor Shaft Applications with High Strength, High Impact Toughness and Excellent Fatigue Life
A steel alloy is disclosed that provides a unique combination of strength, toughness, and fatigue life. The steel alloy has the following composition in weight percent: C about 0.15 to about 0.30 Mn about 1.7 to about 2.3 Si about 0.7 to about 1.1 Cr about 1.85 to about 2.35 Ni about 0.5 to about 0.9 Mo + ½W about 0.1 to about 0.3 Cu about 0.3 to about 0.7 V + 5/9 × Nb about 0.2 to about 0.5 The balance of the alloy is iron, usual impurities, and residual amounts of other elements added during melting for deoxidizing and/or desulfurizing the alloy. A hardened and tempered steel article made from the alloy is also disclosed.
1 . A steel alloy having a unique combination of strength, toughness, and fatigue life, said alloy consisting essentially of, in weight percent,
C
about 0.15 to about 0.30
Mn
about 1.7 to about 2.3
Si
about 0.7 to about 1.1
Cr
about 1.85 to about 2.35
Ni
about 0.5 to about 0.9
Mo + ½W
about 0.1 to about 0.3
Cu
about 0.3 to about 0.7
V + 5/9 × Nb
about 0.2 to about 0.5
and the balance is iron, usual impurities, and residual amounts of other elements added during melting for deoxidizing and/or desulfurizing the alloy.
2 . The steel alloy as claimed in claim 1 which contains at least about 0.18% carbon.
3 . The steel alloy as claimed in claim 1 which contains at least about 1.8% manganese.
4 . The steel alloy as claimed in claim 1 which contains at least about 0.8% silicon.
5 . The steel alloy as claimed in claim 1 which contains at least about 1.95% chromium.
6 . The steel alloy as claimed in claim 1 which contains at least about 0.6% nickel.
7 . The steel alloy as claimed in claim 1 which contains at least about 0.15% Mo+½ W.
8 . The steel alloy as claimed in claim 1 which contains at least about 0.25% (V+( 5/9×Nb)).
9 . The steel alloy as claimed in claim 1 which contains not more than about 0.25% cobalt.
10 . A steel alloy having a unique combination of strength, toughness, and fatigue life, said alloy consisting essentially of, in weight percent,
C
about 0.15 to about 0.27
Mn
about 1.8 to about 2.2
Si
about 0.8 to about 1.0
Cr
about 1.95 to about 2.25
Ni
about 0.6 to about 0.8
Mo + ½W
about 0.15 to about 0.25
Cu
about 0.4 to about 0.6
V + 5/9 × Nb
about 0.25 to about 0.45
and the balance is iron, usual impurities, and residual amounts of other elements added during melting for deoxidizing and/or desulfurizing the alloy.
11 . The steel alloy as claimed in claim 10 which contains at least about 0.21% carbon.
12 . The steel alloy as claimed in claim 10 which contains at least about 1.95% manganese.
13 . The steel alloy as claimed in claim 10 which contains at least about 0.85% silicon.
14 . The steel alloy as claimed in claim 10 which contains at least about 2.05% chromium.
15 . The steel alloy as claimed in claim 10 which contains at least about 0.65% nickel.
16 . The steel alloy as claimed in claim 10 which contains at least about 0.18% Mo+½ W.
17 . The steel alloy as claimed in claim 10 which contains at least about 0.25% (V+( 5/9×Nb)).
18 . The steel alloy as claimed in claim 10 which contains not more than about 0.02% cobalt.
19 . A hardened and tempered steel article formed from a steel alloy consisting essentially of, in weight percent, about
C
about 0.15 to about 0.30
Mn
about 1.7 to about 2.3
Si
about 0.7 to about 1.1
Cr
about 1.85 to about 2.35
Ni
about 0.5 to about 0.9
Mo + ½W
about 0.1 to about 0.3
Cu
about 0.3 to about 0.7
V + 5/9 × Nb
about 0.2 to about 0.5
and the balance is iron, usual impurities, and residual amounts of other elements added during melting for deoxidizing and/or desulfurizing the alloy, said article providing a yield strength of at least about 180 ksi and a Charpy V-notch impact energy of at least about 25 ft-lbs.