U.S. patent application number 13/385816 was filed with the patent office on 2012-10-18 for method for manufacturing of vehicle armor components requiring severe forming with very high bend angles with very thick gauge product of high strength heat treatable aluminum alloys.
Invention is credited to Alex Cho.
Application Number | 20120261039 13/385816 |
Document ID | / |
Family ID | 47005505 |
Filed Date | 2012-10-18 |
United States Patent
Application |
20120261039 |
Kind Code |
A1 |
Cho; Alex |
October 18, 2012 |
Method for manufacturing of vehicle armor components requiring
severe forming with very high bend angles with very thick gauge
product of high strength heat treatable aluminum alloys
Abstract
It has been commonly believed that very thick gauge high
strength aluminum alloy product such as AA2139 plate cannot be
formed to the required sharp angles to form the highly protective
underbody armor for the MRAP vehicles. The present process and
method of manufacture provides a means for strategically combining
the metallurgical process of manufacturing high strength aluminum
alloys and the forming process of V shaped hull to improve the
formability of the very thick gauge high strength alloy product so
much that even the very thick gauge (thicker than 1 inch) plate can
be formed to severe forming angles. This combined process allowed
successful manufacturing of high performance V shaped hulls for the
Mine Resistant Ambush Protected (MRAP) vehicles.
Inventors: |
Cho; Alex; (Lexington,
KY) |
Family ID: |
47005505 |
Appl. No.: |
13/385816 |
Filed: |
March 7, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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61464608 |
Mar 7, 2011 |
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Current U.S.
Class: |
148/697 ;
148/695 |
Current CPC
Class: |
C22F 1/053 20130101;
C22F 1/057 20130101; C21D 9/42 20130101 |
Class at
Publication: |
148/697 ;
148/695 |
International
Class: |
C22F 1/04 20060101
C22F001/04 |
Claims
1. A method of manufacturing highly effective vehicle armor with
very thick gauge high strength heat treatable aluminum alloys by
strategically combining forming process and the metallurgical
process of the alloy a) Thick gauge aluminum alloy products
comprised of the thickness range of from 1 inch to 6 inch thick
product b) High strength heat treatable aluminum alloys comprised
of; i) high strength 2000 series aluminum alloys such as, but not
limited to, AA2139, AA2027, and AA 2519 ii) high strength 7000
series aluminum alloys such as, but not limited to, AA7085 and
AA7081 c) forming process requires solution heat treatment of the
work piece at the solutionization temperature and quench the work
piece to room temperature to condition the work piece to be capable
of receiving severe forming process by bending or bending and
stretching at various bending angles more severe than 160 degrees
of bending angle to meet the geometry requirement of the vehicle
armor component d) If desired, a forming process can add a cold
stretch by a small amount after quench the work piece to further
improve the material properties prior to forming the work piece. e)
The formed armor components can be aged to increase the strength of
the material to take advantage of age hardening characteristics of
heat treatable aluminum alloys.
2. Forming process according to the claim 1, wherein forming the
work piece immediately after solution heat treatment and quench
step to maximize the formability during bend forming or stretch and
bend forming procedure. The solution heat treatment for high
strength 2000 series alloys can be conducted at the temperature
range of 960.degree. F. and 980.degree. F. for the durations to be
adjusted to the thickness of the work piece. The solution heat
treatment for high strength 7000 series alloys can be conducted at
the temperature range of 860.degree. F. and 880.degree. F. for the
durations to be adjusted to the thickness of the work piece.
3. Forming process according to the claim 1, wherein forming the
work piece after solution heat treatment and quench step to
maximize the formability during bend forming or stretch and bend
forming procedure. For very thick plate of 2000 series aluminum
alloys such as 1 inch to 6 inch thick gauge 2139 alloy plate and
2519 alloy plate can be solution heat treated at 960.degree.
F.-980.degree. F. for the duration of 30 minutes to 6 hours
depending on the thickness of the work piece and cold water quench
for conditioning the work piece to be ready for forming operation.
For 2.5 inch thick work piece, 2-4 hours of heat treatment at the
temperature arrange of 960.degree. F.-980.degree. F. would be most
preferred After forming the work piece to the final shape, the work
piece can be age hardened to meet high ballistic and blast
resistance for the armored vehicles. Age hardening can be conducted
at the temperature range of 250-380.degree. F. for the duration of
6 hours to 72 hours depending on the actual age temperatures
selected. This age process can be further modified if required such
as need to compensate the limitation of equipment limitations to
achieve the final age processing effect. A cold stretch of the work
piece by a small amount right after the solution heat treatment can
be a part of the conditioning the work piece for forming operation.
This would further improve the final mechanical properties and
minimize the residual stress of the formed and age hardened work
piece in the final temper condition.
4. Forming process according to the claim 1, wherein forming the
work piece after solution heat treatment and quench step to
maximize the formability during bend forming or stretch and bend
forming procedure. For very thick plate of 7000 series aluminum
alloys such as 1 inch to 6 inch thick gauge 7085 alloy plate and
7081 alloy alloy plate can be solution heat treated at 860.degree.
F.-880.degree. F. and cold water quenched to condition the work
piece to be ready for forming operation. After forming the work
piece to the final shape, the work piece can be age hardened to
meet high ballistic and blast resistance for the armored vehicles.
A cold stretch of the work piece by a small amount right after the
solution heat treatment can be a part of the conditioning the work
piece for forming operation. This would further improve the final
mechanical properties and minimize the residual stress of the
formed and age hardened work piece in the final temper condition.
Description
INTRODUCTION
[0001] A Mine Resistant Ambush Protected (MRAP) vehicle is a family
of armored fighting vehicles designed for the U.S. Army and United
States Marine Corps with the goal of surviving IED attacks and
ambushes--prompted by US deaths in Iraq.
[0002] MRAP vehicles usually have "V" shaped hulls to deflect away
any explosive forces originating below the vehicle, thereby
protecting the vehicle and its passenger compartment. Typically
these explosions are from land mines, but they can also be IEDs
(Improvised Explosive Devices).
BACKGROUND
[0003] Historically the V shaped hulls are made of welded steel
plate, which is very heavy and added much more weight to the
armored vehicles to slow down its mobility and limit the ammunition
and personnel carrying capacity. The vehicle's weight and size
severely limits its mobility off main roads, in urban areas, and
over bridges (reference 1). 72 percent of the world's bridges
cannot hold the MRAP. Its heft also restricts several of the
vehicles from being transported by C-130 cargo aircraft or the
amphibious ships that carry Marine equipment and supplies.
[0004] Instead of steel plate armor, it would be more desirable to
use aluminum alloy plate to make it lighter. Unfortunately, the
traditional aluminum armor alloys such as AA5083 and AA6061 are not
strong enough to provide adequate protection against land mines and
IED's. More recently developed high strength heat treatable
aluminum alloys such as AA2139 and AA2519 among 2000 series alloys
and AA7085 and AA7081 among the 7000 series alloys could meet the
material property requirement for the vehicle armor components and
underbody "V" hull for armored vehicles and MRAPs, respectfully.
Recently, a new aluminum alloy, AA2139, has been developed by Cho
et al. to provide much improved ballistic and mine blast protection
compared to the traditional aluminum alloy based armor plate. The
chemistry of the high strength heat treatable aluminum alloys as
candidate materials for armor plate applications are listed in the
TABLE 1 for AA2139, TABLE 2 for AA2519, TABLE 3 for AA2027, TABLE 4
for AA7085 and TABLE 5 for AA7081.
TABLE-US-00001 TABLE 1 Alloy Chemistry of AA2139 Element wt. % Si
0.1 max Fe 0.15 max Cu 4.5-5.5 Mn 0.20-0.6 Mg 0.20-0.8 Cr 0.05 max
Zn 0.25 max Ti 0.15 max V 0.05 max Ag 0.15-0.6
TABLE-US-00002 TABLE 2 Alloy Chemistry of AA2519 Element wt. % Si
0.25 max Fe 0.30 max Cu 5.3-6.4 Mn 0.10-0.5 Mg 0.05-0.40 Cr 0.05
max Zn 0.10 max Ti 0.01-0.10 V 0.05-0.15 Zr 0.10-0.25
TABLE-US-00003 TABLE 3 Alloy Chemistry of AA2027 Element wt. % Si
0.12 max Fe 0.15 max Cu 3.9-4.9 Mn 0.50-1.2 Mg 1.0-1.5 Cr 0.05 max
Zn 0.20 max Ti 0.08 Zr 0.05-.25
TABLE-US-00004 TABLE 4 Alloy Chemistry of AA7085 Element wt. % Si
0.06 max Fe 0.08 max Cu 1.3-2.0 Mn 0.04 max Mg 1.2-1.8 Cr 0.04 max
Zn 7.0-8.0 Ti 0.06 max Zr 0.06-0.25
TABLE-US-00005 TABLE 5 Alloy Chemistry of AA7081 Element wt. % Si
0.12 max Fe 0.15 max Cu 1.2-1.8 Mn 0.25 max Mg 1.8-2.2 Cr 0.04 max
Zn 6.9-7.5 Ti 0.06 max Zr 0.06-0.25
[0005] The conventional manufacturing method of the "V" hull shaped
underbody armor utilizing high strength alloys consists of welding
two or more number of flat plate together by conventional welding
techniques such as Gas Metal Arc Welding (GMAC) or Friction Stir
welding. Such manufacturing processes increase the cost and lower
the material properties drastically. For example, GMAC process on
high strength, high ballistic performance aluminum alloys would
lower the strength of the welded plate by as much as 70% compared
to the original material properties prior to welding. Friction Stir
welding process could somewhat improve the post-welding strength
compared to that of GMAC process at a much higher cost and gauge
limitations. Yet the post-weld mechanical properties after Friction
Stir Welding (FSW) process is still lower by as much as 35%
compared to the original strength of the alloy prior to welding.
Therefore, the "V" shaped hull manufacturing process consists of
welding processes (GMAW and/or FSW) would degrade the material
properties and severely degrade the protection capability provided
by the V shaped underbody armor against the land mines and IEDs,
which MRAPs are designed for.
SUMMARY OF THE INVENTION
[0006] This application incorporates by reference U.S. Pat. No.
7,229,508, U.S. Pat. No. 6,972,110 and PCT Application Publication
No. WO 2004/090185A1 all of which are incorporated by reference
herein in their entirety. Reference to documents made in the
specification is intended to result in such patents or literature
cited are expressly incorporated herein by reference, including any
patents or other literature references cited within such documents
as if fully set forth in this specification.
[0007] One of the solution to avoid the over weight of MRAP
vehicles due to the over weight of the underbody armor of the "V"
shape hull is to find a manufacturing process of low weight, high
performance underbody armor utilizing high strength, high ballistic
performance aluminum alloys such as high strength 2000 series and
7000 series heat treatable alloys. The preferred solution is to
avoid any welding processes which degrade the properties of the
aluminum alloys significantly. This can be achieved by
manufacturing the "V" shaped hull by forming instead of welding
process. However, "V" shaped hulls for MRAP underbody armor based
on high strength aluminum alloys via. forming process without
welding have not been available to date because of the following
reasons.
1) Highly protective Underbody armor for MRAP vehicles requires
very thick gauge aluminum alloy plate 2) Forming process for highly
protective underbody armor for MRAP requires severe angle of bend
forming to meet the geometry requirement. 3) Forming process of
very thick gauge material to sharp bend angles would require very
high formability of the material 4) High strength, high ballistic
performance aluminum based alloys do not have high formability.
[0008] It has been commonly believed that very thick gauge high
strength aluminum alloy product such as AA2139 plate cannot be
formed to the required sharp angles to form the highly protective
underbody armor for the MRAP vehicles. However, it was unexpectedly
discovered that strategically combining the metallurgical process
of manufacturing high strength aluminum alloys and the forming
process of V shaped hull could improve the formability of the very
thick gauge high strength alloy product so much that even the very
thick gauge (thicker than 1 inch) plate can be formed to severe
forming angles. This combined process allowed successful
manufacturing of high performance V shaped hulls for the Mine
Resistant Ambush Protected (MRAP) vehicles.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] A better understanding of the present invention will be had
upon reference to the following description in conjunction with the
accompanying drawings in which like numerals refer to like parts
throughout the several views and wherein:
[0010] FIG. 1. Picture of the 2.5 inch thick 2139-T8 temper plate
after a bend forming attempt. The plate was fractured at bend angle
of 160 degrees;
[0011] FIG. 2; A schematic diagram of vehicle armor component of
2.5 inch thick AA2139 alloy plate which requires bend angle of 144
degrees, 140 degrees, and 135 degrees;
[0012] FIG. 3; A picture of the successfully formed a vehicle armor
component of 2.5 inch thick AA2139 alloy plate by following the
invented forming process. This part requires bend angle of 144
degrees, 140 degrees, and 135 degrees as shown in FIG. 2;
[0013] FIG. 4; A schematic diagram of vehicle armor component of
2.5 inch thick AA2139 alloy plate which requires bend angle of 135
degrees, 130 degrees, and 125 degrees;
[0014] FIG. 5; A picture of the successfully formed a vehicle armor
component of 2.5 inch thick AA2139 alloy plate by following the
invented forming procedure. This part requires bend angles of 135
degrees, 130 degrees, and 125 degrees as shown in the FIG. 4;
and
[0015] FIG. 6; One example of the underbody armor component design
for armored vehicles which require 125 degree and 140 degree
bending of 2.5 inch thick gauge plate.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
[0016] By strategically combining metallurgical process of
manufacturing high strength heat treatable alloys and bend forming
of very thick gauge work piece, high strength heat treatable alloys
can be formed into various armor components for armored vehicles
even for the parts requiring very thick gauge plate and bend
forming of sharp angles.
[0017] For very thick plate of 2000 series aluminum alloys such as
1 inch to 6 inch thick gauge 2139 alloy plate and 2519 alloy plate
can be solution heat treated at 960.degree. F.-980.degree. F. and
cold water quench for conditioning the work piece to be ready for
forming operation. After forming the work piece to the final shape,
the work piece can be age hardened to meet high ballistic and blast
resistance for the armored vehicles. A cold stretch of the work
piece by a small amount right after the solution heat treatment can
be a part of the conditioning the work piece for forming operation.
This would further improve the final mechanical properties and
minimize the residual stress of the formed and age hardened work
piece in the final temper condition.
[0018] For very thick plate of 7000 series aluminum alloys such as
1 inch to 6 inch thick gauge 7085 alloy plate and 7081 alloy alloy
plate can be solution heat treated at 860.degree. F.-880.degree. F.
and cold water quenched to condition the work piece to be ready for
forming operation. After forming the work piece to the final shape,
the work piece can be age hardened to meet high ballistic and blast
resistance for the armored vehicles. A cold stretch of the work
piece by a small amount right after the solution heat treatment can
be a part of the conditioning the work piece for forming operation.
This would further improve the final mechanical properties and
minimize the residual stress of the formed and age hardened work
piece in the final temper condition.
Example 1
[0019] To examine the forming capability of high strength armor
alloy 2139-T8 plate, a test sample of a 2.5 inch thick.times.5 inch
wide.times.18'' long sample plate was sawed from a commercially
produced large parent plate of 2139-T8 plate delivered from the
plate rolling mill of the Alcan Rolled Products LLC, located at
Ravenswood W. Va. USA. The formability of the 2.5 inch thick
2139-T8 flat plate (180 degree) was formed by a break forming press
with the 16 inch apart two supporting points in the bottom die and
the 4 inch radius of the top die blade. The goal was to bend the
plate to at least 144 degrees to meet the geometry requirement for
the current design of the V shaped hull of an MRAP vehicle.
However, the formability of the 2139-T8 plate was not robust enough
to achieve the required amount of bending. As a result, the sample
plate was fractured at the bending angle of 160 degrees as shown in
the FIG. 1. This test result confirmed that the formability of very
thick gauge 2139-T8 plate is not robust enough to produce the V
shaped very thick gauge high strength aluminum alloy hull of an
MRAP. It is generally known in the professional community skilled
in the art that very thick gauge high strength heat treatable
aluminum alloy plate are not formable.
Example 2
[0020] An ingot of alloy AA2139 was cast in 16 inch thick ingot and
homogenized at 980 F for 24 hours and hot rolled to 2.5 inch gauge
plate in the temperature range of 800 F-900 F and subsequently
followed by solution heat treated at 980 F for 3 hours and cold
water quenched. After cold water quench, the plate was cold
stretched by 3 percent permanent set to condition the plate to be
formed by severe bending. The plate was formed to an armor
component requiring of three bend angles of 144 degrees, 140
degrees and 135 degrees, to make a desirable geometry to make
armored vehicle components. The schematic diagram of the intended
geometry is shown in FIG. 2. FIG. 3 shows the picture of the
component successfully formed to meet the geometry shown in FIG. 2.
The plate is now ready to be aged to the high strength mechanical
property requirement by age process known in the art. The most
typical age process is to heat up the work piece to 320.degree. F.
and soak at the temperature for 36 hours. A variation of thermal
procedures could be utilized at the temperature range of
250.degree.-380.degree. F. for durations selected appropriately to
the temperatures selected.
Example 3
[0021] An ingot of alloy AA2139 was cast in 16 inch thick ingot and
homogenized at 980 F and hot rolled to 2.5 inch gauge plate in the
temperature range of 800 F-900 F and subsequently followed by
solution heat treated at 980 F for 3 hours and cold water quenched.
After cold water quench, the plate was cold stretched by 3 percent
permanent set to condition the plate to achieve high strength after
final heat treatment, and yet be formed by severe bending. The
plate was formed to an armor component requiring of three bend
angles of 135 degrees, 130 degrees and 125 degrees, to make a
desirable geometry to make armored vehicle components. The
schematic diagram of the intended geometry is shown in FIG. 4. FIG.
5 shows the picture of the component successfully formed to meet
the geometry shown in FIG. 4. The plate is now ready to be aged to
the high strength mechanical property requirement by age process
known in the art. The most typical age process is to heat up the
work piece to 320.degree. F. and soak at the temperature for 12-48
hours. A variation of thermal procedures could be utilized at the
temperature range of 250.degree.-380.degree. F. for durations
selected appropriately to the temperatures selected.
Example 4
[0022] FIG. 6 shows one example of the underbody armor component
design for armored vehicles which require 125 degrees and 140
degrees bending of 2.5 inch thick gauge plate.
[0023] Various geometries of highly effective armor components with
very thick gauge high strength aluminum alloys can be manufactured
by utilizing the invented procedure of combination of material
processing steps and forming processes as described above.
Example 5
[0024] An ingot of alloy AA2139 was cast in 16 inch thick ingot and
homogenized at 980 F and hot rolled to 2.0 inch gauge plate in the
temperature range of 800 F-900 F and subsequently followed by
solution heat treated at 980 F for 3 hours and cold water quenched.
After cold water quench, the plate was cold stretched by 3 percent
permanent set to condition the plate to achieve high strength after
final heat treatment, and yet be formed by severe bending. The
plate was formed to an armor component requiring of three bend
angles of 140 degrees, 160 degrees and 160 degrees, to make a
desirable geometry to make armored vehicle components. The formed
parts are age strengthened at 320 F for 24 hours.
Performance Characteristics of the Formed Underbody Armor
[0025] 1. The mechanical properties of the formed underbody armor
after final heat treatment are different from those of flat plate
armor. The three bent areas in the formed underbody armor are very
high in strength due to the high level of cold work (as high as
22%) and provide extremely rigid structural integrity of the
overall armor against the blast force, and the flat portion between
the bent areas are moderately high in strength due to the moderate
level of cold work (nominally 3%) and provide high rupture
resistance with very high fracture toughness. Such a unique
combination of mechanical properties enhances the geometrical
advantage of formed underbody armor as described in above. [0026]
2. The examples of the mechanical properties are listed below from
the sample material processed by the identical manufacturing
procedures as the above manufacturing process specifications.
[0027] a. Mechanical Properties of sample plate representative of
the flat portion between the bent area having nominal 3% cold
work
TABLE-US-00006 [0027] UTS (ksi) TYS (ksi) El (%) K1c (ksi- inch)
68.5 63.5 16 58.1 68.0 63.3 16 54.2
[0028] b. Mechanical Properties of the sample plate having 18% cold
work, representative of the bent area
TABLE-US-00007 [0028] UTS (ksi) TYS (ksi) El (%) K1c (ksi- inch)
75.6 70.7 10 N.A.
[0029] These are very desirable combination of mechanical
properties to ensure superior performance for armor application
compared to the mechanical properties of flat rolled plate of
2139-T8 temper plate per SAE-AMS Specification No. 4468 (see
below)
Mechanical Properties (L Direction) of 2139-T8 Flat Plate per
SAE-AMS Spec 4468
TABLE-US-00008 [0030] UTS (ksi) TYS (ksi) El (%) K1c (ksi- inch) 66
62 9 35
MODIFICATIONS
[0031] Specific compositions, methods, or embodiments discussed are
intended to be only illustrative of the invention disclosed by this
specification. Variation on these compositions, methods, or
embodiments are readily apparent to a person of skill in the art
based upon the teachings of this specification and are therefore
intended to be included as part of the inventions disclosed
herein.
[0032] Reference to documents made in the specification is intended
to result in such patents or literature cited are expressly
incorporated herein by reference, including any patents or other
literature references cited within such documents as if fully set
forth in this specification.
[0033] The foregoing detailed description is given primarily for
clearness of understanding and no unnecessary limitations are to be
understood therefrom, for modification will become obvious to those
skilled in the art upon reading this disclosure and may be made
upon departing from the spirit of the invention and scope of the
appended claims. Accordingly, this invention is not intended to be
limited by the specific exemplifications presented herein above.
Rather, what is intended to be covered is within the spirit and
scope of the appended claims.
* * * * *