US4076525A
Expired / Lapsed
US
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High strength fracture resistant weldable steels
Assignee: Lockheed Martin Corp
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Filing: 1976-07-29
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Granted: 1978-02-28
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Expires: 1996-07-29
Abstract
Abstract A weldable alloy steel having improved fracture toughness and stress corrosion resistance at very high strength levels in which the essential composition, according to percent by weight is in the range of 0.12 - 0.17% carbon, 1.8 - 3.2% chromium, 0.9 - 1.35% molybdenum, 11.5 - 14.5% cobalt, and 9.5 - 10.5% nickel, the remainder being substantially iron, i.e., with minor amounts of certain impurities and residual elements. Very good stress corrosion resistance and fracture toughness at high strength levels is produced when these elements are alloyed in the percent by weight ranges of 0.15 - 0.17% carbon, 1.8 - 2.2% chromium, 0.9 - 1.1% molybdenum, 13.5 - 14.5% cobalt, and 9.5 - 10.5% nickel. Good fatigue endurance is achieved. Minor amounts of manganese also may be present.
Inventors
- 👤 Clayton D. Little
- 👤 Paul M. Machmeier
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 08:48
CPC Classifications
C; C22; C22C; C22C38/00; C22C38/18; C22C38/40; C22C38/52
Claims Analysis
Total Claims: 26
Claim 1
Independent Claim
94 words
A weldable alloy steel having high strength and high fracture toughness consisting essentially of 0.12% - 0.17% carbon, 1.8% - 3.2% chromium, 0.9% - 1.35% molybdenum, 11.5% - 14.5% cobalt, and 9.5% - 10.5% nickel, all as percents by weight, the remainder being iron with minor amounts of impurities and residual elements, said steel having an ultimate tensile strength of from about 220 Ksi to about 270 Ksi, a tensile yield strength of from about 210 Ksi to about 245 Ksi and a fracture toughness (K I .sbsb.C) greater than about 115 Ksi √inch.
Claim 2
Dependent Claim
94 words
A weldable alloy steel having high strength and high fracture toughness consisting essentially of 0.12% - 0.17% carbon, 1.8% - 3.2% chromium, 0.9% - 1.35% molybdenum, 11.5% - 14.5% cobalt, and 9.5% - 10.5% nickel, all as percents by weight, the remainder being iron with minor amounts of impurities and residual elements, said steel having an ultimate tensile strength of from about 220 Ksi to about 270 Ksi, a tensile yield strength of from about 210 Ksi to about 245 Ksi and a fracture toughness (K I .sbsb.C) greater than about 115 Ksi √inch.
Claim 3
Dependent Claim
24 words
The alloy steel of claim 1 in which manganese is present in an amount of from 0.05% to 0.20% by weight of the steel.
Claim 4
Dependent Claim
52 words
The alloy steel of claim 1 in which the most common impurities and residuals are present in amounts not exceeding 0.1% silicon, 0.01% aluminum, 0.01% titanium, 0.005% sulphur, and 0.012% phosphorous, all as percents by weight, and having not more than 40 parts per million nitrogen and 25 parts per million oxygen.
Claim 5
Dependent Claim
27 words
The alloy steel of claim 1 in which said steel is produced by melt processing followed by steps of mechanical working and double austenitizing prior to aging.
Claim 6
Dependent Claim
17 words
The alloy steel of claim 4 in which the melt processing is accomplished using vacuum induction melting.
Claim 7
Dependent Claim
16 words
The alloy steel of claim 5 in which the melt processing further includes vacuum arc remelting.
Claim 8
Dependent Claim
30 words
The alloy steel of claim 4 in which the steel is aged at from about 890° to about 960° F. for from about 1 to about 20 hours total time.
Claim 9
Dependent Claim
42 words
The alloy steel of claim 1 having a stress corrosion resistance (K I .sbsb.SCC) of at least 60 Ksi √inch in the range of 220 Ksi to 270 Ksi tensile ultimate strength when tested for 1,000 hours in 3.5% sodium chloride solution.
Claim 10
Dependent Claim
54 words
The alloy steel of claim 1 which has a stress corrosion resistance (K I .sbsb.SCC) greater than 60 Ksi √inch over a yield strength range of 210-245 Ksi, and which increases with decreasing yield strength (TYS) according to the relationship: K.sub.I.sbsb.SCC = a TYS + b where a = -1.143 and b = 340.
Claim 11
Dependent Claim
41 words
The alloy steel of claim 1 in which the ratio of stress corrosion resistance (K I .sbsb.SCC) to fracture toughness (K I .sbsb.C) is at least about 0.5 when tensile ultimate strength is in the range of 220 Ksi or above.
Claim 12
Dependent Claim
28 words
The alloy steel of claim 1 which exhibits a fatigue endurance limit at 10 7 cycles (R = 0.1, K t = 1) of 110 Ksi or above.
Claim 13
Dependent Claim
42 words
The alloy steel of claim 1 in which the alloying elements are present in the ranges of 0.15% - 0.17% carbon, 13.5% - 14.5% cobalt, 1.8% - 2.2% chromium, 0.9% - 1.1% molybdenum, 9.5% - 10.5% nickel all as percents by weight.
Claim 14
Dependent Claim
24 words
The alloy steel of claim 12 in which manganese is present in an amount of from 0.05% to 0.20% by weight of the steel.
Claim 15
Dependent Claim
51 words
The alloy steel of claim 12 in which the most common impurities and residuals are present in amounts not exceeding 0.1% silicon, 0.01% aluminum, 0.01% titanium, 0.004% sulphur, 0.008% phosphorous and having not more than 20 parts per million nitrogen, 13 parts per million oxygen, and 3 parts per million hydrogen.
Claim 16
Dependent Claim
27 words
The alloy steel of claim 12 in which the steel is produced by melt processing followed by steps of mechanical working and double austenitizing prior to aging.
Claim 17
Dependent Claim
17 words
The alloy steel of claim 15 in which the melt processing is accomplished using vacuum induction melting.
Claim 18
Dependent Claim
16 words
The alloy steel of claim 16 in which the melt processing further includes vacuum arc remelting.
Claim 19
Dependent Claim
29 words
The alloy steel of claim 15 in which the steel is aged at from about 900°to about 950° F. for from about 1 to about 20 hours total time.
Claim 20
Dependent Claim
35 words
The alloy steel of claim 12 which has an ultimate tensile strength of from about 235 Ksi to about 270 Ksi and a tensile yield strength of from about 220 Ksi to about 245 Ksi.
Claim 21
Dependent Claim
19 words
The alloy steel of claim 19 having a fracture toughness (K I .sbsb.C) greater than about 125 Ksi √inch.
Claim 22
Dependent Claim
46 words
The alloy steel of claim 19 having a stress corrosion resistance (K I .sbsb.SCC) of at least about 70 Ksi √inch in the range of from about 235 Ksi to about 270 Ksi tensile ultimate strength when tested for 1,000 hours in 3.5% sodium chloride solution.
Claim 23
Dependent Claim
63 words
The alloy steel of claim 21 which has a stress corrosion resistance (K I .sbsb.SCC) greater than about 70 Ksi √inch over a yield strength range of from about 220 Ksi to about 245 Ksi, and which increases with decreasing yield strength (TYS) according to the relationship: K i .sbsb.scc = a TYS + b where: a = -1.143 and b = 350.
Claim 24
Dependent Claim
42 words
The alloy steel of claim 19 in which the ratio of stress corrosion resistance (K I .sbsb.SCC) to fracture toughness (K I .sbsb.C) is at least about 0.6 when tensile ultimate strength is in the range of about 235 Ksi or above.
Claim 25
Dependent Claim
29 words
The alloy steel of claim 19 which exhibits a fatigue endurance limit at 10 7 cycles (R = 0.1, K t = 1) of about 150 Ksi or above.
Claim 26
Dependent Claim
49 words
The alloy steel of claim 14 in which there are additional residuals which when present do not exceed the following amounts: vanadium -- 0.02%, tin -- 0.002%, lead -- 0.002%, zirconium -- 0.002%, boron -- 0.0005% and rare earths -- 0.01%, all as percents by weight of the steel.
References Cited (Backward Citations)
USRE28523E
Cited
US3502462A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1981-02-27 | 1981-08-29 | 1982-02-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-02-27 | 1985-08-29 | 1986-02-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-02-27 | 1989-08-29 | 1990-02-28 | $7700.00 | Window Closed / Lapsed |