Quench and temper corrosion resistant steel alloy
A quench and temper steel alloy is disclosed having the following composition in weight percent. C 0.2-0.5 Mn 0.1-1.0 Si 0.1-1.2 Cr 9-14.5 Ni 2.0-5.5 Mo 1-2 Cu 0-1.0 Co 1-4 W 0.2 max. V 0.1-1.0 Ti up to 0.5 Nb 0-0.5 Ta 0-0.5 Al 0-0.25 Ce 0-0.01 La 0-0.01 The balance of the alloy is iron and the usual impurities including not more than about 0.01% phosphorus, not more than about 0.010% sulful, and not more than about 0.10% nitrogen. A quenched and tempered steel article made from this alloy is also disclosed. The steel article is characterized by a tensile strength of at least about 290 ksi, a fracture toughness (k Ic ) of at least about 65 ksi, good resistance to general corrosion, and good resistance to pitting corrosion.
1. A steel alloy consisting essentially of, in weight percent, about
C
0.35-0.45
Mn
0.1-0.7
Si
0.1-1.0
Cr
9.5-12.5
Ni
3.2-4.3
Mo
1.25-1.75
Cu
0.1-1.0
Co
2-3
W
up to 0.05
V
0.3-0.6
Ti
0.01-0.2
Nb
up to 0.01
Ta
up to 0.01
Al
0.01 max.
Ce
0-0.006
La
0-0.005
and the balance is iron and impurities wherein phosphorus is restricted to not more than about 0.005%, sulfur is restricted to not more than about 0.001%, and nitrogen is restricted to not more than about 0.03%.
2. The alloy set forth in claim 1 wherein copper is not more than about 0.7%.
3. The alloy set forth in claim 1 wherein copper is at least about 0.3%.
4. A quenched and tempered steel article made from the alloy set claim 1 which has a tensile strength of at least 290 ksi.
5. The steel article set forth in claim 4 which has a fracture toughness (K Ic ) of at least about 65 ksi√in when tested in accordance with ASTM Standard Test Procedure E1290.
6. The steel article set forth in claim 5 which has sufficient general corrosion resistance such that the article does not rust after 200 hours when tested in accordance with ASTM Standard Test procedure B 117.
7. The steel article as set forth in claim 5 which has sufficient pitting corrosion resistance such that the article has a pitting potential of at least 90 mV when tested in accordance with ASTM Standard Test procedure G61 modified by using round bar samples.
8. A structural component for an aerospace vehicle wherein the component is made from an alloy consisting essentially of, in weight percent, about
C
0.35-0.45
Mn
0.1-0.7
Si
0.1-1.0
Cr
9.5-12.5
Ni
3.2-4.3
Mo
1.25-1.75
Cu
0.1-0.7
Co
2-3
W
0.1 max.
V
0.3-0.6
Ti
0.01-0.2
Nb
0.01 max.
Ta
0.01 max.
Al
0.01 max.
Ce
0-0.006
La
0-0.005
and the balance is iron and impurities wherein phosphorus is restricted to not more than about 0.005%, sulfur is restricted to not more than about 0.0005%, and nitrogen is restricted to not more than about 0.03%.
9. The aerospace structural component as set forth in claim 8 wherein the component is selected from the group consisting of one or more of landing gear, a rotatable shaft, an actuator, flap tracks, and slat tracks.