U.S. patent application number 09/789409 was filed with the patent office on 2001-10-11 for high strength, chromium-and lithium-free aluminum casting alloy and related vehicular structural components.
Invention is credited to Fang, Que-Tsang, Shabel, Barrie S..
Application Number | 20010028860 09/789409 |
Document ID | / |
Family ID | 26750580 |
Filed Date | 2001-10-11 |
United States Patent
Application |
20010028860 |
Kind Code |
A1 |
Fang, Que-Tsang ; et
al. |
October 11, 2001 |
High strength, chromium-and lithium-free aluminum casting alloy and
related vehicular structural components
Abstract
There is claimed a high strength, aluminum alloy composition
especially suited for cast vehicular structural components. This
chromium- and lithium-free, alloy consists essentially of: about
3-3.6 wt. % zinc, about 1.3-1.6 wt. % magnesium, about 0.2-0.8 wt.
% manganese, about 0.08-0.16 wt. % zirconium, up to about 0.3 wt. %
copper, up to about 0.15 wt. % silicon, and up to about 0.25 wt. %
iron, the balance aluminum, incidental elements and impurities. It
exhibit a typical tensile yield strength greater than about 29 ksi
without having to undergo T6-type thermal processing.
Inventors: |
Fang, Que-Tsang; (Export,
PA) ; Shabel, Barrie S.; (Murrysville, PA) |
Correspondence
Address: |
ALCOA INC
ALCOA TECHNICAL CENTER
100 TECHNICAL DRIVE
ALCOA CENTER
PA
15069-0001
US
|
Family ID: |
26750580 |
Appl. No.: |
09/789409 |
Filed: |
February 20, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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|
09789409 |
Feb 20, 2001 |
|
|
|
09211555 |
Dec 15, 1998 |
|
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60069933 |
Dec 17, 1997 |
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Current U.S.
Class: |
420/532 |
Current CPC
Class: |
C22C 21/10 20130101 |
Class at
Publication: |
420/532 |
International
Class: |
C22C 021/10 |
Claims
What is claimed is:
1. A high strength, chromium- and lithium-free aluminum alloy
product cast from a composition consisting essentially of: about
3-3.6 wt. % zinc, about 1.3-1.6 wt. % magnesium, about 0.2-0.8 wt.
% manganese, about 0.08-0.16 wt. % zirconium, up to about 0.3 wt. %
copper, up to about 0.15 wt. % silicon, and up to about 0.25 wt. %
iron, the balance aluminum, incidental elements and impurities.
2. The cast alloy product of claim 1 which contains less than about
3.4 wt. %zinc.
3. The cast alloy product of claim 1 which contains greater than
about 1.4 wt. % magnesium.
4. The cast alloy product of claim 1 which contains greater than
about 0.4 wt. % manganese.
5. The cast alloy product of claim 1 which contains greater than
about 0.1 wt. % zirconium.
6. The cast alloy product of claim 1 which contains less than about
0.1 wt. % silicon and less than about 0.15 wt. % iron.
7. The cast alloy product of claim 1 which is capable of achieving
a typical tensile yield strength greater than about 29 ksi without
having to undergo T6-type thermal processing.
8. A chromium-free, lithium-free aluminum cast product which has an
ultimate tensile strength of about 40 ksi or higher without having
been solution heat treated, said casting consisting essentially of:
about 3-3.6 wt. % zinc, about 1.3-1.6 wt. % magnesium, about
0.2-0.8 wt. % manganese, about 0.08-0.16 wt. % zirconium, up to
about 0.3 wt. % copper, up to about 0.15 wt. % silicon, and up to
about 0.25 wt. % iron, the balance aluminum, incidental elements
and impurities.
9. The cast product of claim 8 which contains less than about 3.4
wt. % zinc.
10. The cast product of claim 8 which contains greater than about
1.4 wt. % magnesium.
11. The cast product of claim 8 which contains greater than about
0.4 wt. % manganese.
12. The cast product of claim 8 which contains greater than about
0.1 wt. % zirconium.
13. The cast product of claim 8 which contains less than about 0.1
wt. % silicon and less than about 0.15 wt. % iron.
14. A vehicular structural component made from a chromium-free,
lithium-free, aluminum casting alloy consisting essentially of:
about 3-3.6 wt. % zinc, about 1.3-1.6 wt. % magnesium, about
0.2-0.8 wt. % manganese, about 0.08-0.16 wt. % zirconium, up to
about 0.3 wt. % copper, up to about 0.15 wt. % silicon, and up to
about 0.25 wt. % iron, the balance aluminum, incidental elements
and impurities, said structural component exhibiting a typical
tensile yield strength greater than about 29 ksi without having to
undergo T6-type thermal processing.
15. The cast structural component of claim 14 which contains less
than about 3.4 wt. % zinc.
16. The cast structural component of claim 14 which contains
greater than about 1.4 wt. % magnesium.
17. The cast structural component of claim 14 which contains
greater than about 0.4 wt. % manganese.
18. The cast structural component of claim 14 which contains
greater than about 0.1 wt. % zirconium.
19. The cast structural component of claim 14 which contains less
than about 0.1 wt. % silicon and less than about 0.15 wt. %
iron.
20. The cast structural component of claim 14 which is a suspension
part.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of U.S. patent
application Ser. No. 09/211,555, filed Dec. 15, 1998, which
application claims the benefit of U.S. Provisional Application Ser.
No. 60/069,933, filed on Dec. 17, 1997, the disclosure of which is
fully incorporated by reference herein.
BACKGROUND OF THE INVENTION
[0002] This invention provides an improved aluminum casting alloy
that possesses high strengths without the need for solution heat
treatments. Most conventional aluminum casting alloys, like A356
and A357 (Aluminum Association designations) require a T6 type heat
treatment to obtain properties with an average ultimate tensile
strength (UTS) greater than 40 ksi, an average yield strength (YS)
greater than 29 ksi and an average elongation greater than 8%. The
T6 heat treatment or tempering process typically involves solution
heat treatment (or "solutionizing") at a high temperature between
530-540.degree. C., water quenching down from that temperature, and
artificial aging. It is a costly and time consuming process due to
capital and space requirements, operation cost, part distortion and
subsequent wastewater treatment. An aluminum casting alloy that
doesn't require a T6-type heat treatment, especially the solution
heat treatment portion thereof, while achieving comparable
properties would be highly desired from a significant cost savings
standpoint.
[0003] Numerous aluminum-zinc alloys have been patented over the
years. These include: U.S. Pat. Nos. 2,388,563, 2,506,788,
3,287,185, 4,874,578 and 5,620,652, just to name a few.
SUMMARY OF THE INVENTION
[0004] The above objectives of this invention are achieved by way
of a chromium- and lithium-free alloy composition that consists
essentially of: about 3.0-3.6 wt. % zinc, about 1.3-1.6 wt %
magnesium, about 0.2-0.8 wt. % manganese, about 0.08-0.16 wt. %
zirconium, up to about 0.3 wt. % copper, up to about 0.15 wt. %
silicon, and up to about 0.25 wt. % iron, the balance aluminum,
incidental elements and impurities. One preferred aluminum casting
composition according to this invention consists essentially of 3.2
wt. % zinc, 1.45 wt. % magnesium, 0.55 wt. % manganese, 0.12 wt %
zirconium, 0.08 wt. % silicon and 0.11 wt % iron. This new
generation casting alloy composition contains no purposeful
additions of such elements as chromium, lithium, nickel, and
vanadium, thereby distinguishing it from other known casting
alloys. Particularly, it has been observed that when small amounts
of such elements as Cr were added to the aformentioned composition,
no positive property effects were observed. With the foregoing
composition, however, castings made from this alloy are able to
achieve a typical T6-type tensile yield strength of greater than
about 29 ksi WITHOUT having to undergo typical T6 type thermal
processing.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0005] Unless indicated otherwise, all composition percentages set
forth herein are by weight. As used herein, the term "substantially
free" means that no purposeful additions of that alloying element
were made, but that due to the presence of impurities and/or
leaching from prolonged contact with manufacturing equipment, trace
quantities of such elements may, nevertheless, find their way into
the final alloy product so cast according to the present
invention.
[0006] The term "minimum" strength (or other measurable
property/characteristic) refers to that level which can be
guaranteed such that about 99% of the product is expected to
conform with 95% confidence at that level using standard
statistical methods. "Typical" strengths tend to run a little
higher than the minimum guaranteed levels associated with plant
production but they are a worthwhile approximation when
insufficient commercial values exist with which to perform a
standard statistical calculation. Typical strengths also serve to
illustrate an invention's relative improvement in strength when
comparing same to established strength values of the prior art.
This invention, for example, is able to achieve typical T6-aged,
tensile yield strengths of greater than about 29 ksi, often about
33 ksi or higher, without having to undergo typical T6 type thermal
processing, as that term is generally defined for a given aluminum
alloy product by the Aluminum Association.
[0007] When referring to any numerical range of values herein, such
ranges are understood to include each and every number and/or
fraction between the stated range minimum and maximum. A range of
about 3.0-3.6 wt. % zinc, for example, would expressly include all
intermediate values of about 3.1, 3.2 and 3.3%, all the way up to
and including 3.55, 3.57 and 3.59% Zn. The same applies to each
other numerical property and/or elemental range set forth
herein.
[0008] The alloy composition of this invention can be used in sand
or permanent molds, die cast, squeeze cast, or subject to other
comparable casting processes. Parts made with this alloy can be
artificially aged for 1 to 24 hours at one or more temperatures
between 100-200.degree. C., in a single or multi-step process, but
they need not be solution heat treated beforehand. With the
foregoing representative composition, a single step aging for 4
hours at 350.degree. F. resulted in an average UTS/YS/elongation of
40 ksi, 30 ksi and 16%, respectively. The same composition
subjected to a two step age of 2 hours at 250.degree. F., followed
by 3 hours at 350.degree. F., resulted in average UTS/YS/elongation
values of 42 ksi, 33 ksi and 16%, or roughly the "equivalent" of
maximum values for A356 alloys aged to a T6 temper. With these
values, the compositions of this invention are suitable for
manufacturing into suspension parts and other vehicular, especially
automotive, structural components.
[0009] Distinct differences often exist between cast and wrought
aluminum alloy products. Registrations for the respective
compositions are separately addressed by the Aluminum Association
with cast alloys being designated in three digits as compared to
the four digit designations for wrought alloy products. Not all
wrought alloy compositions have a cast equivalent either. Sometimes
subtle differences enable one alloy product to be made by only one
of these principal methods and not the other. Further processing,
SHT, quenching, thermo-mechanical aging, etc., does not always
translate well between product forms. For example, in U.S. Pat. No.
3,790,219, it was observed that cast Al alloy wheels may not
withstand the stresses of their wrought "equivalents", wheels which
have been shaped by pressing or spinning from rolled sheet, or
forged from a cast billet.
[0010] Having described the presently preferred embodiments, it is
to be understood that this invention may be otherwise embodied in
the scope of the claims appended hereto.
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