CROSS REFERENCE TO RELATED APPLICATION
BACKGROUND OF THE INVENTION
1. Field of Invention
[0002] The present invention relates to an aluminum alloy designed to consume high levels
of post-consumer recycled material while still meeting or exceeding all the requirements
for use in the general engineering market. The alloy is surprisingly resilient and
maintains excellent mechanical properties, machinability characteristics while still
maintaining reasonable thermal stability performance.
2. Description of Related Art
[0003] There is currently a wide scale initiative to improve sustainability in a number
of different industries and one path to improved sustainability is through increased
recycling. In the aluminum industry, increasing the amount of post-consumer recycled
aluminum greatly reduces the amount of energy that is required to make a given product.
This is due to the fact that it takes significantly more energy to refine aluminum
ore into pure aluminum than it does to melt recycled material. Per the European Aluminum
association, producing one kilogram of prime aluminum creates approximately 18 kg
of CO
2 equivalents; however by utilizing post consumer scrap the CO
2 emissions are lowered significantly. If instead 100% post consumer scrap was utilized,
the emissions generated from remelting that scrap and casting an ingot or billet could
be as low as 0.5 kg of CO
2 equivalents per kg of aluminum. That is a greater than 97% reduction in emissions
by utilizing 100% scrap. As seen from the emissions data there is a significant environmental
benefit to increasing the percentage of scrap in a given product as much as possible.
[0004] However, there are some complications that come with trying to increase the amount
of scrap in a given composition. One of the biggest issues is the difficulty in keeping
aluminum scrap segregated. Typically, any post consumer scrap that is available is
going to be a mix of different alloys. For example, a common source of post-consumer
scrap is shredded cars, the aluminum portion of which is more commonly known as twitch.
This type of scrap can contain numerous different aluminum alloys including 4xxx series
castings, 5xxx series body sheet, 6xxx series extrusion and finally 7xxx series extrusions.
This type of scrap can also contain zinc or magnesium castings depending on how well
the various pieces of the vehicle are separated prior to shredding. Without further
processing this type of scrap can only be used in limited quantities because of the
typical composition or impurity limits for most registered alloys.
[0005] One method for addressing this issue is by improving the sorting of the post-consumer
aluminum scrap. There are current technologies for separating aluminum from other
metals or any other contaminants such as wood or plastic. Some sorting technologies
can even take mixed aluminum scrap and separate it into groups containing only a single
alloy family to further improve the amount of scrap that can be utilized. However,
the more sorting that is required the more time, cost and energy that is being invested
into the scrap.
[0006] Another method of improving the post-consumer scrap utilization in the production
of aluminum products is to increase the tolerance of the alloy to impurity elements.
This limits the amount of sorting that is required and also increases the amount and
types of scrap that can be utilized. Under optimal conditions this type of alloy can
be produced with 100% post consumer scrap. This can be accomplished by thoughtfully
adjusting the composition limits to tailor the performance of the material to match
the use case.
BRIEF SUMMARY OF THE INVENTION
[0007] The present invention is directed to a 6xxx alloy that is capable of being produced
with high amounts of recycled content. A preferred application for this 6xxx alloy
is in the general engineering market with a specific focus on rod and bar products
which benefit significantly from excellent machinability performance.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The features and advantages of the present invention will become apparent from the
following detailed description of a preferred embodiment thereof, taken in conjunction
with the accompanying drawings, in which:
FIG. 1 shows the mechanical properties from example 1;
FIG. 2 shows the typical grain structure from example 2;
FIG. 3 shows the anodize response from example 3 with Inventive Alloy (left) compared
to 6061 (right);
FIG. 4 shows typical chips produced in turn operation on 1" rod; and
FIG. 5 shows parts produced during machinability testing of 2" rod.
DETAILED DESCRIPTION OF THE INVENTION
[0009] The present invention is directed to a 6xxx series aluminum alloy composition comprising,
or consisting essentially of, or consisting of (by weight %): 0.50 - 1.50% Si, 0.10
- 0.70% Cu, 0.50 - 1.50% Mg, 0.05 - 0.35% Cr, 0.30 - 1.20% Zn; allowable impurities
including ≤ 0.80% Fe, ≤ 0.80% Mn, ≤0.15% Ti, ≤0.15% Zr, and unavoidable impurities
to ≤ 0.05% each and ≤0.15% total unavoidable impurities with the remainder being aluminum.
The inventive alloy is capable of being produced utilizing high amounts of post-consumer
recycled material while still achieving the performance required for use in the general
engineering market.
[0010] In an alternate embodiment, the 6xxx series aluminum alloy composition comprising,
or consisting essentially of, or consisting of (by weight %): 0.8-1.4% Si, 0.1-0.7%
Cu, 0.8-1.4% Mg, 0.3-1.1% Zn, 0.05-0.30% Cr, ≤0.6% Fe, ≤0.8% Mn, ≤0.15% Zr, ≤0.15%
Ti, and unavoidable impurities limited to ≤0.05% each and ≤0.15% total with the balance
being aluminum.
[0011] The addition of Mg increases the strength of aluminum alloys, especially when combined
with the addition of Si. These two elements combine to form a precipitate known as
Mg
2Si. This phase is a significant contributor to material strength in precipitation
hardening elements. In addition, multiple other precipitation hardening phases are
formed due to the high number of alloying elements present in this composition. These
additional phases include MgZn
2 as well as Al
2CuMg, which is more commonly known as S-Phase. The ratio of these phases will depend
on the relative amounts of Mg, Si and Zn that are present in a given composition.
Mg
2Si will form preferentially as compared to MgZn
2 and as such, MgZn
2 will only form if there is enough Mg leftover after the formation of the Mg
2Si phase. As these are the primary strengthening phases present in this alloy the
relative amounts of these elements need to be controlled to achieve optimal strength
in this type of composition.
[0012] The addition of Cr is done to restrict recrystallization in this structure. Fully
unrecrystalized structures are preferred in these applications as the presence of
recrystallized grains can lead to poor machinability performance in certain machining
operations. The Cr forms a dispersoid (Al12Mg2Cr) phase which restricts recrystallization.
This phase helps to limit recrystallization by limiting the grain boundary movement.
Limiting the amount of coarse grain present in this material helps to achieve optimal
material performance.
[0013] It is understood that the ranges identified above for the 6xxx series aluminum alloy
composition includes the upper or lower limits for the element selected and every
numerical range provided within the range may be considered as upper or lower limits.
For example, it is understood that within the range of 0.5 - 1.5 wt.% Si, the upper
or lower limit for Si may be selected from 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2,
1.3, 1.4 and 1.5 wt.%. In addition, for example, it is understood that within the
range of 0.1 - 0.7 wt.% Cu, the upper or lower limit for Cu may be selected from 0.1,
0.2, 0.3, 0.4, 0.5, 0.6, 0.7 wt.%. In addition, for example, it is understood that
within the range of 0.5 - 1.5 wt.% Mg, the upper or lower limit for Mg may be selected
from 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4 and 1.5 wt.%. In addition, for
example it is understood that within the range of 0.05 - 0.35 wt.% Cr, the upper or
lower limit for Cr may be selected from 0.08, 0.11, 0.14, 0.17, 0.20, 0.23, 0.26,
0.29, 0.32, and 0.35 wt.%. In addition, for example, it is understood that within
the range of 0.3 - 1.2 wt.% Zn, the upper or lower limit for Zn may be selected from
0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, and 1.2 wt.%. In addition, for example,
it is understood that within the range of allowable impurities of ≤ 0.8 wt.% Fe, the
upper limit for Fe may be selected from 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, and 0.1
wt.%. In addition, for example, it is understood that within the range of allowable
impurities of ≤ 0.8 wt.% Mn, the upper limit for Mn may be selected from 0.8, 0.7,
0.6, 0.5, 0.4, 0.3, 0.2, and 0.1 wt.%. In addition, for example, it is understood
that within the range of allowable impurities of ≤ 0.15 wt.% Ti, the upper limit for
Ti may be selected from 0.15, 0.14, 0.13, 0.12, 0.11, 0.10, 0.09, 0.08, 0.07, 0.06,
0.05, 0.04, 0.03, 0.02, and 0.01 wt.%. In addition, for example, it is understood
that within the range of allowable impurities of ≤ 0.15 wt.% Zr, the upper limit for
Zr may be selected from 0.15, 0.14, 0.13, 0.12, 0.11, 0.10, 0.09, 0.08, 0.07, 0.06,
0.05, 0.04, 0.03, 0.02, and 0.01 wt.%. It is further understood that any and all permutations
of the range identified above are included within the scope of the present invention.
[0014] The 6xxx series aluminum alloy composition of the present invention may also include
low level of "unavoidable impurities" that are not included intentionally. The "unavoidable
impurities" means any other elements except the above described Al, Si, Cu, Mg, Cr,
Zn, Fe, Mn, Ti, and Zr. It is understood that the range of to ≤ 0.05 wt.% each and
≤ 0.15 wt.% total unavoidable impurities, includes the upper or lower limit ≤ 0.05,
≤ 0.04, ≤ 0.03, ≤ 0.02, and ≤ 0.01 wt.% each unavoidable impurities, and 0.15, 0.14,
0.13, 0.12, 0.11, 0.10, 0.09, 0.08, 0.07, 0.06, 0.05, 0.04, 0.03, 0.02, and 0.01 wt.
% total unavoidable impurities.
[0015] In a preferred embodiment the 6xxx series aluminum alloy composition is manufactured
by 1) casting using conventional direct chill casting methods; 2) then homogenizing
at 950 °F to 1060 °F (510 - 571 °C) for 2 to 10 hours; 3) then preheating to 800 °F
- 1000 °F (427 - 538 °C) and then hot working; followed by water quenching, optionally
stretching for stress relief and straightening, and artificially aging at a temperature
between 250 - 375 °F for 6 - 20 hours. The 6xxx series aluminum alloy compositions
may be subjected to hot working operation, such as extrusion, forging or rolling.
A preferred hot working operation is extrusion.
[0016] In another preferred embodiment the 6xxx series aluminum alloy composition is manufactured
by 1) casting using conventional direct chill casting methods; 2) then optionally
homogenizing at 950 °F to 1060 °F (510 - 571 °C) for 2 to 10 hours; 3) then preheating
to a rolling temperature of 600 °F - 1000 °F (316 - 538 °C) and then hot rolling;
followed by solution heat treatment at a temperature of 950
0F to 1070
0F, followed by quenching to room temperature, optionally stretching for stress relief
and straightening, and artificially aging at a temperature between 250 - 375 °F for
6 - 20 hours.
[0017] In another preferred embodiment the 6xxx series aluminum alloy composition is manufactured
by 1) casting using conventional direct chill casting methods; 2) then homogenizing
at 950 °F to 1060 °F (510 - 571 °C) for 2 to 10 hours; 3) then preheating to an extrusion
temperature of 450 °F - 1000 °F (232 - 538 °C) and then extruding; optionally drawing
the extrusions; followed by solution heat treatment at a temperature of 950
0F to 1070
0F, followed by quenching to room temperature, optionally stretching for stress relief
and straightening, and artificially aging at a temperature between 250 - 375 °F for
6 - 20 hours.
[0018] The final product including the 6xxx series aluminum alloy composition may be a rod,
bar, extruded shape, sheet, and/or plate with a thickness of 0.25 - 10 inches. The
final product including the 6xxx series aluminum alloy preferably has tensile yield
strengths in excess of 295 MPa (43 ksi), or in excess of 300 MPa, or in excess of
310 MPa, or in excess of 325 MPa, or in excess of 330 MPa, or in excess of 339 MPa.
In addition to improved tensile yield strength, the final product including the 6xxx
series aluminum alloy may have Ultimate Tensile Strength in excess of 340 MPa, or
in excess of 345 MPa, or in excess of 349 MPa, or in excess of 355 MPa, or in excess
of 360 MPa, or in excess of 364 MPa.
[0019] The 6xxx series aluminum alloy composition may be produced with greater than 75%
scrap, or greater than 80% scrap, or greater than 85 % scrap, or greater than 90 %
scrap, or greater than 95 % scrap, or with 100% scrap. The scrap used may include,
but is not limited to, post-consumer scrap and/or post-industrial scrap. When using
greater than 75% scrap to produce the 6xxx series aluminum alloy composition of the
present invention, the final product may have excellent machinability performance
as defined by achieving a B grade or better in the ASM machinability test detailed
in Figure 1 of chapter on Machining of Aluminum and Aluminum Alloys in the ASM Handbook
Aluminum and Aluminum Alloys (1993 Revision and Publication), the contents of which
are expressly incorporated herein by reference.
[0020] The following examples illustrate various aspects of the invention and are not intended
to limit the scope of the invention.
Example 1:
[0021] Extrusion billets were cast in 10" (253 mm) diameter using convention direct chill
casting methods. The composition of these billets is shown in Table 1.
Table 1: Compositions of Alloys Studied in Example 1 |
Alloy |
Si |
Fe |
Cu |
Mn |
Mg |
Zn |
Cr |
Ti |
1350 |
1.01 |
0.28 |
0.62 |
0.57 |
0.95 |
0.41 |
0.15 |
0.02 |
1357 |
1.43 |
0.22 |
0.30 |
0.57 |
1.06 |
0.79 |
0.14 |
0.00 |
[0022] The billets were then homogenized at 950 - 1060 °F (510 - 571 °C) for 2 - 10 hours.
These billets were then preheated to 800 °F - 1000 °F (427 - 538 °C) and extruded.
All samples were then water quenched from the hot working operation. After quenching
samples were aged at 250 - 375 °F for 6 - 20 hours. After aging the mechanical properties
of the samples were evaluated to determine the potential strength levels that these
types of compositions can achieve. The results of the mechanical property evaluation
is shown in Table 2.
Table 2: Mechanical Properties of Alloys in Example 1 |
Composition |
YTS [MPa] |
YTS [ksi] |
UTS [MPa] |
UTS [ksi] |
Elong. |
6061 AA Minimum |
241 |
35 |
262 |
38 |
10 |
1350 |
340.1 |
49.3 |
369.1 |
53.5 |
12.2 |
1350 |
340.5 |
49.4 |
366.5 |
53.2 |
11.6 |
1350 |
341.3 |
49.5 |
366.2 |
53.1 |
12.4 |
1350 |
338.6 |
49.1 |
364.7 |
52.9 |
12.3 |
1350 |
339.6 |
49.3 |
364.9 |
52.9 |
11.5 |
1357 |
327.7 |
47.5 |
353.1 |
51.2 |
12.4 |
1357 |
326.3 |
47.3 |
350.7 |
50.9 |
11.8 |
1357 |
327.1 |
47.4 |
351.7 |
51.0 |
12.5 |
1357 |
325.6 |
47.2 |
350.9 |
50.9 |
11.7 |
1357 |
325.1 |
47.2 |
349.4 |
50.7 |
11.6 |
[0023] This shows that these types of compositions are capable of achieving strengths well
in excess of what is necessary in the general engineering market, as demonstrated
by the difference in properties to a typical general engineering alloy 6061.
Example 2:
[0024] Extrusion billets were produced in 12" (305 mm) and 18" (457 mm) diameter using conventional
direct chill casting methods. The compositions of these billets are shown in Table
3.
Table 3: Compositions of Alloys Studied in Example 3 |
Alloy |
Diameter |
Si |
Fe |
Cu |
Mn |
Mg |
Zn |
Cr |
Ti |
1681 |
12" |
0.78 |
0.44 |
0.30 |
0.60 |
0.78 |
0.49 |
0.10 |
0.02 |
1683 |
12" |
1.04 |
0.42 |
0.61 |
0.58 |
0.56 |
0.49 |
0.10 |
0.02 |
1684 |
12" |
0.79 |
0.44 |
0.31 |
0.60 |
1.21 |
0.51 |
0.10 |
0.02 |
1687 |
12" |
1.30 |
0.43 |
0.30 |
0.60 |
1.19 |
0.50 |
0.10 |
0.02 |
1691 |
12" |
1.28 |
0.43 |
0.30 |
0.60 |
0.80 |
0.53 |
0.10 |
0.02 |
1698 |
12" |
1.03 |
0.43 |
0.29 |
0.58 |
0.99 |
0.50 |
0.09 |
0.01 |
1699 |
12" |
1.05 |
0.42 |
0.30 |
0.57 |
1.01 |
1.00 |
0.09 |
0.02 |
1717 |
18" |
1.05 |
0.44 |
0.30 |
0.60 |
1.00 |
0.49 |
0.09 |
0.02 |
[0025] All material was homogenized at 950 - 1060 °F (510 - 571 °C) for 2 - 10 hours. Then
the 12" diameter billets were preheated to 800 °F - 1000 °F (427 - 538 °C) and extruded
into 1" (25.3 mm) and 2" (50.6 mm) diameter rod as well as 2"x3" (50.6 mm x 76.2 mm)
rectangular bar. The 18" material was preheated to the same temperature and extruded
into 8" (203 mm) diameter rod as well as 4"x6" (102 mm x 152 mm) rectangular bar.
The material was then water quenched from the hot working operation and aged at 250
- 375 °F for 6 - 20 hours.
[0026] The resultant material demonstrated an excellent combination of tensile properties
and machinability performance. The average yield and ultimate strengths for each composition
and product combination can be seen in Table 4 and Table 5. Again, the improvement
in strengths relative to the minimum requirements of a typical general engineering
alloy like 6061 listed in Table 2 must be noted.
Table 4: Mechanical Properties of Products Extruded from 12" Diameter Billets |
|
Avg. YTS [ksi] |
Avg. UTS [ksi] |
Avg. Elong. |
Alloy |
1" |
2" |
2"x3" |
1" |
2" |
2"x3" |
1" |
2" |
2"x3" |
1681 |
50.45 |
49.10 |
50.15 |
54.85 |
53.75 |
54.65 |
13.63 |
13.03 |
12.60 |
1683 |
53.30 |
55.38 |
52.25 |
56.68 |
58.93 |
55.98 |
12.58 |
10.50 |
11.50 |
1684 |
47.80 |
49.80 |
47.55 |
53.18 |
55.30 |
53.10 |
12.80 |
13.20 |
12.65 |
1687 |
52.75 |
54.93 |
53.40 |
55.93 |
58.38 |
56.60 |
11.45 |
11.48 |
10.93 |
1691 |
54.15 |
56.45 |
53.23 |
57.88 |
60.58 |
57.38 |
12.35 |
11.08 |
12.68 |
1698 |
52.40 |
56.28 |
51.58 |
56.00 |
60.03 |
55.43 |
11.98 |
11.83 |
11.73 |
1699 |
55.90 |
55.87 |
55.33 |
59.45 |
60.07 |
59.15 |
11.88 |
11.50 |
12.08 |
Table 5: Mechanical Properties of Products Extruded from 18" Diameter Billets |
|
Avg. YTS [ksi] |
Avg. UTS [ksi] |
Avg. Elong. |
Alloy |
4"x6" |
8" |
4"x6" |
8" |
4"x6" |
8" |
1717 |
50.23 |
47.83 |
54.55 |
52.78 |
9.85 |
10.23 |
[0027] The machinability performance of this material was evaluated by performing a number
of different common machining operations on the samples and assessing the resultant
chips to determine the size and weight characteristics. Smaller overall chips result
in improved machining operations as it minimizes issues with the processes by reducing
the amount of large messy tangled masses of machining chips. When this occurs, manual
intervention by the operator is required to resolve this resulting in equipment downtime.
The machining performance of these alloys is detailed in the following tables that
show the total chips per gram produced in the various machining operations. These
results are equivalent to achieving a grade of B or better in the ASM Handbook machinability
test (1993 Revision and Publication).
Table 6: Machinability Results of Products Extruded from 12" Diameter Billet |
|
1" Diameter |
2" Diameter |
2"x3" Rec Bar |
Alloy |
Drill |
Cutoff |
Turn |
Form |
Drill |
Cutoff |
Turn |
Form |
Drill |
Mill |
0.25" Mill |
1681 |
2.12 |
2.38 |
4.33 |
2.34 |
2.32 |
0.39 |
0.23 |
0.99 |
8.31 |
19.38 |
44.41 |
1683 |
2.56 |
2.10 |
4.25 |
5.01 |
3.05 |
0.63 |
1.15 |
2.04 |
10.24 |
18.76 |
58.01 |
1684 |
2.51 |
2.48 |
2.27 |
2.92 |
2.13 |
0.99 |
0.52 |
3.34 |
8.00 |
18.71 |
57.41 |
1687 |
2.58 |
2.64 |
4.39 |
8.53 |
3.32 |
0.79 |
0.69 |
1.55 |
10.80 |
18.65 |
60.60 |
1691 |
2.08 |
2.25 |
2.69 |
8.09 |
3.08 |
0.60 |
0.64 |
0.54 |
7.13 |
18.40 |
62.73 |
1698 |
2.71 |
2.89 |
3.67 |
7.05 |
2.88 |
0.59 |
0.61 |
2.23 |
8.68 |
19.10 |
53.99 |
1699 |
2.78 |
1.97 |
3.57 |
6.91 |
3.19 |
1.07 |
0.98 |
3.57 |
10.46 |
18.58 |
58.01 |
Table 7: Machinability Results of Products Extruded from 18" Diameter Billet |
|
4"x6" Rec Bar |
8" Diameter |
Alloy |
Long Drill |
Short Drill |
0.250 Drill |
End Mill - Long |
End Mill Short |
OD Turn |
Drill |
ID Turn |
Groove |
1717 |
9.28 |
9.53 |
78.27 |
17.86 |
16.86 |
19.13 |
5.57 |
11.89 |
0.27 |
[0028] The grain structure developed in these extruded products was unrecrystalized with
minimal to no peripheral coarse grain (PCG). Peripheral coarse grain is a thin band
of coarse recrystallized grains that appear on the outer perimeter of a profile with
an otherwise unrecrystalized grain structure. A typical example of the grain structure
in the 2" diameter rod product can be seen in FIG. 2.
[0029] Samples were also anodized to compare the performance to that of typical 6061 material.
The overall anodize were quite good and in line with the performance that can be expected
from 6061 when it is being anodized. The anodize performance compared to 6061 material
can be seen in FIG. 3.
[0030] Overall this demonstrates these compositions ability to achieve excellent mechanical
property and machinability while maintain good anodizing performance with an unrecrystalized
grain structure with minimal PCG.
Example 3:
[0031] The compositions shown in the table below were cast and extruded as per the previous
example with some of the compositions being produced in 12" (305 mm) and some being
produced in 18" (457 mm).
Table 8: Compositions of Alloys Studied in Example 3 |
Alloy |
Diameter |
Si |
Fe |
Cu |
Mn |
Mg |
Zn |
Cr |
Ti |
1771 |
12" |
1.30 |
0.45 |
0.30 |
0.60 |
1.21 |
0.52 |
0.16 |
0.02 |
1772 |
12" |
0.89 |
0.48 |
0.29 |
0.58 |
0.90 |
0.49 |
0.16 |
0.02 |
1773 |
12" |
1.09 |
0.46 |
0.30 |
0.60 |
1.04 |
0.50 |
0.17 |
0.02 |
1774 |
18" |
1.10 |
0.44 |
0.29 |
0.59 |
1.05 |
0.51 |
0.17 |
0.02 |
[0032] The amount of scrap utilized in each charge when producing these compositions was
tracked and the percentage breakdown of scrap vs. prime in each charge is included
in the following table.
Table 9: Charge Makeup for Casts Complete in Example 3 |
Alloy |
% Scrap in Charge |
% Prime in Charge |
1771 |
97.14 |
2.86 |
1772 |
100.00 |
0.00 |
1773 |
100.00 |
0.00 |
1774 |
100.00 |
0.00 |
[0033] Again, as per the previous example, this material was homogenized at 950 - 1060 °F
(510 - 571 °C) for 2 - 10 hours. The billets were preheated to 800 °F - 1000 °F (427
- 538 °C) and the 12" diameter billets were extruded into 1" (25.3 mm) and 2" (50.6
mm) diameter rod as well as 2"x3" (50.6 mm x 76.2 mm) rectangular bar while the 18"
diameter billets were extruded into 8" (203 mm) diameter rod as well as 4"x6" (102
mm x 152 mm) rectangular bar. The material was quenched and aged with the same practices
that were utilized in the previous example.
[0034] The mechanical properties and machinability performance of this material as again
evaluated through the same test methods as the previous example. The results of the
testing were in line with the previous material performance over the range of sizes
and compositions evaluated. These results are detailed in the following tables.
Table 10: Mechanical Properties of Products Extruded from 12" Diameter Billets |
|
Avg. YTS [ksi] |
Avg. UTS [ksi] |
Avg. Elong. |
Alloy |
1" |
2" |
2"x3" |
1" |
2" |
2"x3" |
1" |
2" |
2"x3" |
1771 |
53.43 |
54.35 |
51.70 |
56.60 |
57.55 |
55.03 |
11.18 |
11.78 |
12.03 |
1772 |
52.81 |
50.51 |
49.80 |
56.49 |
54.49 |
54.33 |
12.09 |
12.36 |
11.65 |
1773 |
52.68 |
53.88 |
51.70 |
56.28 |
57.08 |
55.50 |
11.55 |
12.75 |
10.73 |
Table 11: Mechanical Properties of Products Extruded from 18" Diameter Billets |
|
Avg. YTS [ksi] |
Avg. UTS [ksi] |
Avg. Elong. |
Alloy |
4"x6" |
8" |
4"x6" |
8" |
4"x6" |
8" |
1774 |
48.70 |
48.38 |
53.35 |
53.05 |
9.78 |
9.35 |
Table 12: Machinability Results of Products Extruded from 12" Diameter Billets |
|
1" Diameter |
2" Diameter |
2"x3" Rec Bar |
Alloy |
Drill |
Cutoff |
Turn |
Form |
Drill |
Cutoff |
Turn |
Form |
Drill |
Mill |
0.25" Mill |
1771 |
4.93 |
3.31 |
7.56 |
10.28 |
3.08 |
1.25 |
1.03 |
2.22 |
5.23 |
14.00 |
29.28 |
1772 |
2.99 |
2.33 |
7.21 |
5.39 |
2.29 |
0.70 |
0.38 |
2.47 |
3.94 |
13.84 |
23.39 |
1773 |
3.42 |
2.82 |
7.95 |
7.12 |
3.09 |
0.74 |
0.74 |
2.24 |
5.22 |
13.85 |
26.17 |
Table 13: Machinability Results of Products Extruded from 18" Diameter Billets |
|
4"x6" Rec Bar |
8" Diameter |
Alloy |
Long Drill |
Short Drill |
0.250 Drill |
End Mill - Long |
End Mill Short |
OD Turn |
Drill |
ID Turn |
Groove |
1774 |
5.00 |
5.14 |
29.53 |
15.56 |
14.87 |
21.71 |
4.94 |
15.73 |
0.09 |
[0035] All casts in this evaluation were produced with scrap making up more than 90% of
the charge showing that these properties can be achieved while using high levels of
scrap material in the production process.
Example 4:
[0036] Rolling ingots were produced in 23"x46" (584 mm x 1168 mm) using conventional direct
chill casting methods. The compositions for the ingots are included in Table 14.
Table 14: Compositions of Alloys Studied in Example 4 |
Alloy |
Si |
Fe |
Cu |
Mn |
Mg |
Zn |
Cr |
Ti |
1781 |
0.90 |
0.41 |
0.28 |
0.56 |
0.88 |
0.47 |
0.15 |
0.02 |
1789 |
1.09 |
0.37 |
0.35 |
0.54 |
0.99 |
0.48 |
0.12 |
0.02 |
1791 |
1.31 |
0.44 |
0.30 |
0.59 |
1.21 |
0.53 |
0.16 |
0.02 |
[0037] These ingots were then homogenized at 950 - 1060 °F (510 - 571 °C) before being rolled
into 1" (25.3 mm) thick plate. After rolling the plates were solution heat treat between
950 - 1150 °F (510 - 621 °C) before being quenched. Finally, the plates were aged
at 250 - 375 °F for 6 - 20 hours.
[0038] After completion of aging tensile samples were taken from the plates and the results
of the mechanical property testing can be seen in the following table.
Table 15: Mechanical Properties of Plate Products Produced in Example 4 |
|
Avg. YTS [ksi] |
Avg. UTS [ksi] |
Avg. Elong. |
Alloy |
LT Orientation |
LT Orientation |
LT Orientation |
1781 |
50.30 |
53.10 |
9.60 |
1789 |
48.90 |
52.80 |
8.40 |
1791 |
46.60 |
50.50 |
11.70 |
[0039] This example demonstrates that these compositions are capable of achieving the same
mechanical properties when produced in a rolled product as compared to an extruded
product.
[0040] While specific embodiments of the invention have been disclosed, it will be appreciated
by those skilled in the art that various modifications and alterations to those details
could be developed in light of the overall teachings of the disclosure. Accordingly,
the particular arrangements disclosed are meant to be illustrative only and not limiting
as to the scope of the invention which is to be given the full breadth if the appended
claims and any and all equivalents thereof.
1. A 6xxx series aluminum alloy having a composition comprising, (by weight %):
0.5-1.5% Si;
0.1-0.7% Cu;
0.5-1.5% Mg;
0.3-1.2% Zn;
0.05-0.35% Cr;
≤0.8% Fe;
≤0.8% Mn;
≤0.15% Zr;
≤0.15% Ti;
with other elements restricted as unavoidable impurities limited to ≤0.05% each and
≤0.15% total with the balance being aluminum.
2. The 6xxx series aluminum alloy of claim 1 comprising,
0.8-1.4% Si;
0.1-0.7% Cu;
0.8-1.4% Mg;
0.3-1.1% Zn;
0.05-0.30% Cr;
≤0.6% Fe;
≤0.8% Mn;
≤0.15% Zr;
≤0.15% Ti.
3. The 6xxx series aluminum alloy of claim 1 or claim 2 including greater than 75% scrap.
4. The 6xxx series aluminum alloy of claim 1 or claim 2 including greater than 90% scrap.
5. An extruded, forged or rolled product manufactured from the 6xxx series aluminum alloy
of any one of claims 1-4 having a yield tensile strength greater than 295 MPa (42.8
ksi).
6. An extruded, forged or rolled product manufactured from the 6xxx series aluminum alloy
of any one of claims 1-4 having a yield tensile strength greater than 320 MPa (46.4
ksi).
7. An extruded, rolled or forged product manufactured from the 6xxx series aluminum alloy
of any one of claims 1-6 having excellent machinability performance as defined by
achieving a B grade or better in the ASM machinability test.
8. An extruded, rolled or forged product manufactured from the 6xxx series aluminum alloy
of any one of claims 1-7 having a thickness of 0.25- 10 inches.
9. An extruded, rolled or forged product manufactured from the 6xxx series aluminum alloy
of claim 8 having a thickness of 1-10 inches.
10. A method of manufacturing the 6xxx series aluminum alloy of any one of claims 1-9
comprising,
a) casting using conventional direct chill casting methods;
b) homogenizing at 950 °F to 1060 °F (510 - 571 °C) for 2 to 10 hours;
c) preheating to 800 °F - 1000 °F (427 - 538 °C);
d) hot working by extrusion, forging or rolling;
e) water quenching;
f) optionally stretching for stress relief and straightening, and
g) artificially aging at a temperature between 250 - 375 °F for 6 - 20 hours.
11. A method of manufacturing the 6xxx series aluminum alloy of claim 10, wherein said
hot working is extrusion.
12. A method of manufacturing the 6xxx series aluminum alloy of any one of claims 1-9
comprising,
a) casting using conventional direct chill casting methods;
b) optionally homogenizing at 950 °F to 1060 °F (510 - 571 °C) for 2 to 10 hours;
c) preheating to a rolling temperature of 600 °F - 1000 °F (316 - 538 °C);
d) hot rolling;
e) solution heat treatment at a temperature of 9500F to 10700F,
f) quenching to room temperature,
g) optionally stretching for stress relief and straightening, and
h) artificially aging at a temperature between 250 - 375 °F for 6 - 20 hours.
13. A method of manufacturing the 6xxx series aluminum alloy of any one of claims 1-9
comprising,
a) casting using conventional direct chill casting methods;
b) homogenizing at 950 °F to 1060 °F (510 - 571 °C) for 2 to 10 hours;
c) preheating to an extrusion temperature of 450 °F - 1000 °F (232 - 538 °C) and then
extruding;
d) optionally drawing the extrusions;
e) solution heat treatment at a temperature of 9500F to 10700F,
f) quenching to room temperature,
g) optionally stretching for stress relief and straightening, and
h) artificially aging at a temperature between 250 - 375 °F for 6 - 20 hours.