US4477292A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Three-step aging to obtain high strength and corrosion resistance in Al-Zn-Mg-Cu alloys
Assignee: Alcoa Corp
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Filing: 1981-10-15
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Granted: 1984-10-16
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Expires: 2001-10-15
Abstract
Abstract A three-step thermal aging method for improving the strength and corrosion resistance of an article comprising a solution heat treated aluminum alloy containing zinc, magnesium, copper and at least one element selected from the group consisting of chromium, manganese and zirconium. The article is precipitation hardened at about 175 DEG to 325 DEG F., heat treated for from several minutes to a few hours at a temperature of about 360 DEG to 390 DEG F. and again precipitation hardened at about 175 DEG to 325 DEG F. In a preferred embodiment the article treated comprises aluminum alloy 7075 in the T6 condition. The method of the invention is easier to control and is suitable for treating articles of greater thickness than other comparable methods.
Inventors
- 👤 Melvin H. Brown
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 07:54
CPC Classifications
C; C22; C22F; C22F1/00; C22F1/04
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
135 words
In a method for heat treating an article comprising a solution heat treated aluminum alloy of the 7000 series, said alloy containing aluminum, zinc, magnesium, copper and at least one element selected from the group consisting of chromium, manganese and zirconium, said method comprising the steps of (a) precipitation hardening the article at about 175° to 325° F.; (b) heat treating the article by immersing it in a heat treating medium; and (c) precipitation hardening the article at about 175° to 325° F.; the improvement wherein step (b) is carried out for about 10 minutes to a few hours at a temperature of about 360° to 375° F., said method thereby being suitable for treatment of articles having greater maximum thickness than methods in which step (b) is carried out at greater than 390° F.
Claim 2
Dependent Claim
135 words
In a method for heat treating an article comprising a solution heat treated aluminum alloy of the 7000 series, said alloy containing aluminum, zinc, magnesium, copper and at least one element selected from the group consisting of chromium, manganese and zirconium, said method comprising the steps of (a) precipitation hardening the article at about 175° to 325° F.; (b) heat treating the article by immersing it in a heat treating medium; and (c) precipitation hardening the article at about 175° to 325° F.; the improvement wherein step (b) is carried out for about 10 minutes to a few hours at a temperature of about 360° to 375° F., said method thereby being suitable for treatment of articles having greater maximum thickness than methods in which step (b) is carried out at greater than 390° F.
Claim 3
Dependent Claim
32 words
The method of claim 1 wherein step (b) is carried out at a time and temperature within the perimeter of ABCDE of FIG. 1 and consistent with the limitations of claim 1.
Claim 4
Dependent Claim
24 words
The method of claim 2 wherein step (b) is carried out at a temperature of about 375° F. for about 45 to 90 minutes.
Claim 5
Dependent Claim
17 words
The method of claim 1 wherein step (b) is carried out for about 10 to 150 minutes.
Claim 6
Dependent Claim
22 words
The method of claim 1 wherein step (a) is carried out for about 24 hours at a temperature of about 250° F.
Claim 7
Dependent Claim
26 words
The method of claim 5 wherein step (c) is carried out for about 6 to 12 hours at a temperature of about 275° to 300° F.
Claim 8
Dependent Claim
20 words
The method of claim 1 wherein steps (a) and (c) are each carried out for about 2 to 30 hours.
Claim 9
Dependent Claim
52 words
The method of claim 1 wherein the maximum thickness of said article in inches is given by the formula ##EQU2## wherein T is the temperature in degrees Fahrenheit of the heat treating medium, and h T is the coefficient of heat transfer between the heat treating medium and the article in BTU/(hr)(sq.ft.)(deg.F.).
Claim 10
Dependent Claim
38 words
The method of claim 8 wherein the heat treating medium is air, and at least a portion of the article has a maximum thickness of about 3.0 inches at 370° F. and about 4.1 inches at 360° F.
Claim 11
Dependent Claim
39 words
The method of claim 8 wherein the heat treating medium is mineral oil, and at least a portion of the article has a maximum thickness of about 10.5 inches at 370° F. and about 14.5 inches at 360° F.
Claim 12
Dependent Claim
40 words
The method of claim 8 wherein the heat treating medium is a molten metal, and at least a portion of the article has a maximum thickness of about 37.8 inches at 370° F. and about 52.3 inches at 360° F.
Claim 13
Dependent Claim
111 words
In a method for heat treating an article comprising a solution heat treated aluminum 7075 alloy, said method comprising the steps of (a) precipitation hardening the article for about 24 hours at about 250° F.; (b) heat treating the article by immersing it in a heat treating medium; and (c) precipitation hardening the article for about 6 to 12 hours at about 275° to 300° F.; the improvement wherein step (b) is carried out for about 45 to 90 minutes at about 375° F., said method thereby being suitable for treatment of articles having greater maximum thickness than methods in which step (b) is carried out at greater than 390° F.
Claim 14
Dependent Claim
111 words
In a method for heat treating an article comprising a solution heat treated aluminum 7075 alloy, said method comprising the steps of (a) precipitation hardening the article for about 24 hours at about 250° F.; (b) heat treating the article by immersing it in a heat treating medium; and (c) precipitation hardening the article for about 6 to 12 hours at about 275° to 300° F.; the improvement wherein step (b) is carried out for about 45 to 90 minutes at about 375° F., said method thereby being suitable for treatment of articles having greater maximum thickness than methods in which step (b) is carried out at greater than 390° F.
Claim 15
Dependent Claim
13 words
The method of claim 1 wherein said article comprises an aluminum 7075 alloy.
References Cited (Backward Citations)
US3856584A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1987-10-16 | 1988-04-16 | 1988-10-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-10-16 | 1992-04-16 | 1992-10-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-10-16 | 1996-04-16 | 1996-10-16 | $7700.00 | Window Closed / Lapsed |