Note: Descriptions are shown in the official language in which they were submitted.
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HEAT TREATED ALUMINUM SHEETS AND PROCESSES FOR MAKING
Cross-Reference to Related Application
[0001] This application claims the benefit of U.S. Provisional
Application No.
63/263,052, filed October 26,2021, which is incorporated herein by reference
in its entirety.
Technical Field
[0002] The present disclosure relates to metal processing generally and
more
specifically to continuous heat treatment processes for metals, where a strip
of a heat
treatable alloy is solutionized, rapidly cooled, thermally spiked, and coiled.
Background
[0003] Manufacturers of metal articles are faced with the challenge of
providing thin
gauge materials that have both good formability and high strength after an
article has been
formed and paint-cured. As one example, the automobile industry requires such
products for
use in body panels or structural members with reduced weight for improving
vehicle
economy and fuel efficiency.
[0004] Heat-treatable metals, such as heat-treatable aluminum alloys,
can, in some
cases, achieve these objectives. Heat-treatable alloys are generally those
containing soluble
alloying constituents in amounts that exceed their room temperature solubility
limits. These
alloys can contain hardening elements (e.g., Mg, Si and/or Co) to provide
hardening during
aging, and potentially other elements, like Fe, Mn and possibly Cr, to control
the formability
and grain size. Such alloys may develop enhanced properties upon being
subjected to
working and/or heating, followed by a quenching step. Heat treatment of metals
is
traditionally performed by precipitation hardening involving the steps of
solution heat
treatment and aging. In a solution heat treatment process, a metal strip,
e.g., an aluminum
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alloy strip, is solutionized, rapidly cooled and, may or may not be thermally
spiked,
depending on the product requirements. The purpose of the solutionizing
procedure is to take
the alloying (solute) elements into solution, which will eventually strengthen
the particular
alloy. The purpose of the rapid cooling is to lock the solute elements and
excess vacancies
into the metal (e.g., aluminum) matrix of the metal strip. The purpose of
thermal spiking is to
ensure that the coil is coiled between 60 C to 110 C and to eliminate the
adverse effect of
coil storage during which material loses potential strength gain during paint
bake of up to
40%. The heat treated metal strip can then undergo an aging procedure.
[0005] As an example, the current process to produce age tempers,
requires a batch
ageing process where a coil in the T4 temper is heated at 20 C/h to 50 C/h
to an elevated
temperature ranging from 120 C to 260 C, soaked for >1 hour, and cooled to
room
temperature. However, the existing thermal treatment and batch aging processes
require total
cycle times longer than 8 hours plus soak time (>1 hour, often 4-6 hours),
added steps and
complexity, and precise control over the heat treatment process.
Summary
[0006] The term embodiment and like terms are intended to refer broadly
to all of the
subject matter of this disclosure and the claims below. Statements containing
these terms
should be understood not to limit the subject matter described herein or to
limit the meaning
or scope of the claims below. Embodiments of the present disclosure covered
herein are
defined by the claims below, not this summary. This summary is a high-level
overview of
various aspects of the disclosure and introduces some of the concepts that are
further
described in the Detailed Description section below. This summary is not
intended to
identify key or essential features of the claimed subject matter, nor is it
intended to be used in
isolation to determine the scope of the claimed subject matter. The subject
matter should be
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understood by reference to appropriate portions of the entire specification of
this disclosure,
any or all drawings and each claim.
[0007] Certain aspects and features of the present disclosure relate to a
continuous
heat treatment process, where a metal strip is solutionized, rapidly cooled,
thermally spiked at
an elevated temperature ranging from 120 C to 300 C (e.g., from 200 C to
250 C), and
coiled at the rewind located at the end of the continuous line. In some
aspects, the continuous
heat treatment process and its constituent steps can occur at a particular
line speed, for
example a line speed of at least 10 meters/min (e.g., at least 40 meters/min;
from 10
meters/min to 100 meters/min, from 40 meters/min to 100 meters/min, or from 10
meters/min
to 40 meters/min). In some aspects, the thermal spike treatment can occur in a
relatively long
reheater furnace, for example a reheater furnace longer than 10 meters. In
some aspects, only
natural cooling (i.e., no cooling apparatus is used) occurs between thermal
spiking and
coiling and coiling is carried out in a such a way as to maintain the line
speed. In some
aspects, the cooling or natural cooling rate after thermal spike treatment is
less than 10
C/hour (e.g., less than 2 C/hour) down to ambient temperature, for example.
Therefore, in
some aspects, the coiling of the metal strip is performed at a relatively warm
temperature, for
example at a temperature above 60 C, such as above 110 C, from 70 C to 150
C, from 70
C to 130 C, or from 70 C to 110 C, from 110 C to 150 C, from 110 C to
130 C, or
from 110 C to 120 C, for example. In certain aspects, the disclosed process
does not
include or need a batch aging process to age harden the material.
[0008] The present disclosure is able to produce a product from the
disclosed process
with thin gauge that has both good formability and high strength using a
continuous
annealing line without requiring a batch ageing process. The disclosure is
particularly
beneficial in terms of offering products with tailored combination of
properties and hence
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offering the possibility of downgauging or as a potential substitute for 5000
series aluminum
alloys supplied in H1X, H2X and H3x tempers.
Detailed Description
[0009] Certain aspects and features of the present disclosure relate to a
continuous
heat treatment process, where a metal strip is solutionized, rapidly cooled,
thermally spiked
(e.g., by hot air) at an elevated temperature ranging from 120 C to 300 C,
coiled, and cooled
or naturally cooled (before and/or after coiling), for example at a rate of
less than or equal to
C/hour, preferably at a rate less than or equal to 2 C/hour. In certain
embodiments, the
metal strip is a heat treatable alloy, for example, a heat treatable aluminum
alloy.
[0010] In certain embodiments, the thermal spike temperature is kept
between 120 C
and 300 C (e.g., from about 150 C to 300 C). The use of thermal spike at
higher
temperature can induce the formation of clusters which act as nuclei to form
hardening
particles during subsequent coiling and coil cooling.
[0011] The present disclosure improves over existing technology in part
by
eliminating the batch process altogether by using a reheater furnace to
thermally spike a
metal strip to a desired temperature at the speed of the line before coiling.
For example, a
continuous annealing line can be used without requiring a batch aging process.
The
thermally spiked coil in combination with coil cooling provides appropriate
conditions for
age hardening. The use of thermal spiking and coiling at warm coiling
temperatures to tailor
a variety of properties is achieved by the present disclosure. The disclosure
is particularly
beneficial in terms of offering products with tailored combination of
properties and hence
offering the possibility of downgauging.
[0012] Aspects and features of the present disclosure are described
herein with
respect to metal strips, such as continuously-cast or uncoiled metal strips,
however the
present disclosure can also be used with any suitable metal products processed
on a
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continuous annealing line. The aspects and features of the present disclosure
can be
especially suitable for any metal product having flat surfaces. The aspects
and features of the
present disclosure can be especially suitable for any metal product having
parallel or
approximately parallel opposing surfaces (e.g., top and bottom surfaces).
Approximately
parallel can include parallel or within 10, 20, 30, 40, 50, 60, 70, 80, 9 ,
or 10 of parallel, or
more.
Definitions and Descriptions
[0013] As used herein, the terms "invention," "the invention," "this
invention" and
"the present invention" are intended to refer broadly to all of the subject
matter of this patent
application and the claims below. Statements containing these terms should be
understood
not to limit the subject matter described herein or to limit the meaning or
scope of the patent
claims below.
[0014] In this description, reference is made to alloys identified by AA
numb ers and
other related designations, such as "series" or "7xxx." For an understanding
of the number
designation system most commonly used in naming and identifying aluminum and
its alloys,
see "International Alloy Designations and Chemical Composition Limits for
Wrought
Aluminum and Wrought Aluminum Alloys" or "Registration Record of Aluminum
Association Alloy Designations and Chemical Compositions Limits for Aluminum
Alloys in
the Form of Castings and Ingot," both published by The Aluminum Association.
[0015] As used herein, a plate generally has a thickness of greater than
about 15 mm.
For example, a plate may refer to an aluminum product having a thickness of
greater than
about 15 mm, greater than about 20 mm, greater than about 25 mm, greater than
about 30
mm, greater than about 35 mm, greater than about 40 mm, greater than about 45
mm, greater
than about 50 mm, or greater than about 100 mm.
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[0016] As used herein, a shate (also referred to as a sheet plate)
generally has a
thickness of from about 4 mm to about 15 mm. For example, a shate may have a
thickness of
about 4 mm, about 5 mm, about 6 mm, about 7 mm, about 8 mm, about 9 mm, about
10 mm,
about 11 mm, about 12 mm, about 13 mm, about 14 mm, or about 15 mm.
[0017] As used herein, a sheet generally refers to an aluminum product
having a
thickness of less than about 4 mm. For example, a sheet may have a thickness
of less than
about 4 mm, less than about 3 mm, less than about 2 mm, less than about 1 mm,
less than
about 0.5 mm, or less than about 0.3 mm (e.g., about 0.2 mm).
[0018] As used herein, a foil generally refers to a metal product having
a thickness
less than about 0.2 mm. For example, a foil may have a thickness of less than
about 0.2 mm,
less than about 0.15 mm, less than about 0.10 mm, less than about 0.05 mm,
less than about
0.04 mm, less than about 0.03 mm, less than about 0.02 mm, or less than about
0.01 mm
(e.g., about 0.006 mm).
[0019] As used herein, direct chill (DC) and continuous casting are two
methods of
casting solid metal from liquid metal. In DC casting, liquid metal is poured
into a mold
having a retractable false bottom capable of withdrawing at the rate of
solidification of the
liquid metal in the mold, often resulting in a large and relatively thick
ingot (e.g., 1 500 mm
wide x 500 mm thick x 5 m long). The ingot can be processed, homogenized, hot
rolled, cold
rolled, may or may not be annealed after hot rolling or before a final cold
rolling pass, and/or
heat treated, and otherwise finished before being coiled into a metal strip
product
distributable to a consumer of the metal strip product (e.g., an automotive
manufacturing
facility).
[0020] Continuous casting involves continuously injecting molten metal
into a casting
cavity defined between a pair of moving opposed casting surfaces and
withdrawing a cast
metal form (e.g., a metal strip) from the exit of the casting cavity.
Continuous casting has
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been desirable in instances where the entire product can be prepared in a
single, fully-coupled
processing line. Such a fully-coupled processing line involves matching, or
"coupling," the
speed of the continuous casting equipment to the speed of the downstream
processing
equipment.
[0021] Reference may be made in this application to alloy temper or
condition. For
an understanding of the alloy temper descriptions most commonly used, see
"American
National Standards (ANSI) H35 on Alloy and Temper Designation Systems." An F
condition
or temper refers to an aluminum alloy as fabricated. An 0 condition or temper
refers to an
aluminum alloy after annealing. An Hxx condition or temper, also referred to
herein as an H
temper, refers to a non-heat treatable aluminum alloy after cold rolling with
or without
thermal treatment (e.g., annealing). Suitable H tempers include HX1, HX2, HX3
HX4, HX5,
HX6, HX7, HX8, or HX9 tempers. A Ti condition or temper refers to an aluminum
alloy
cooled from hot working and naturally aged (e.g., at room temperature). A T2
condition or
temper refers to an aluminum alloy cooled from hot working, cold worked and
naturally
aged. A T3 condition or temper refers to an aluminum alloy solution heat
treated, cold
worked, and naturally aged. A T4 condition or temper refers to an aluminum
alloy solution
heat treated and naturally aged. A T5 condition or temper refers to an
aluminum alloy cooled
from hot working and artificially aged (at elevated temperatures). A T6
condition or temper
refers to an aluminum alloy solution heat treated and artificially aged. A T7
condition or
temper refers to an aluminum alloy solution heat treated and artificially
overaged. A T8x
condition or temper refers to an aluminum alloy solution heat treated, cold
worked, and
artificially aged. A T9 condition or temper refers to an aluminum alloy
solution heat treated,
artificially aged, and cold worked. A W condition or temper refers to an
aluminum alloy
after solution heat treatment.
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[0022] As used herein, the meaning of "room temperature" can include a
temperature
of from about 15 C to about 30 C, for example about 15 C, about 16 C,
about 17 C,
about 18 C, about 19 C, about 20 C, about 21 C, about 22 C, about 23 C,
about 24 C,
about 25 C, about 26 C, about 27 C, about 28 C, about 29 C, or about 3 0
C. As used
herein, the meaning of "ambient conditions" or "ambient environment" can
include
temperatures of about room temperature, relative humidity of from about 20% to
about
100%, and barometric pressure of from about 975 millibar (mbar) to about 1050
mb ar. For
example, relative humidity can be about 20%, about 21%, about 22%, about 23%,
about 24%,
about 25%, about 26%, about 27%, about 28%, about 29%, about 30%, about 31%,
about
32%, about 33%, about 34%, about 35%, about 36%, about 37%, about 38%, about
39%,
about 40%, about 41%, about 42%, about 43%, about 44%, about 45%, about 46%,
about
47%, about 48%, about 49%, about 50%, about 51%, about 52%, about 53%, about
54%,
about 55%, about 56%, about 57%, about 58%, about 59%, about 60%, ab out 61%,
about
62%, about 63%, about 64%, about 65%, about 66%, about 67%, about 68%, about
69%,
about 70%, about 71%, about 72%, about 73%, about 74%, about 75%, about 76%,
about
77%, about 78%, about 79%, about 80%, about 81%, about 82%, about 83%, about
84%,
about 85%, about 86%, about 87%, about 88%, about 89%, about 90%, about 91%,
about
92%, about 93%, about 94%, about 95%, about 96%, about 97%, about 98%, about
99%,
about 100%, or anywhere in between. For example, barometric pressure can be
about 975
mbar, about 980 mbar, about 985 mbar, about 990 mbar, about 995 mbar, about
1000 mbar,
about 1005 mbar, about 1010 mbar, about 1015 mbar, about 1020 mbar, about 1025
mbar,
about 1030 mbar, about 1035 mbar, about 1040 mbar, about 1045 mbar, about 1050
mbar, or
anywhere in between.
[0023] All ranges disclosed herein are to be understood to encompass any
and all
subranges subsumed therein. For example, a stated range of "1 to 10" should be
considered
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to include any and all subranges between (and inclusive of) the minimum value
of 1 and the
maximum value of 10; that is, all subranges beginning with a minimum value of
1 or more,
e.g., 1 to 6.1, and ending with a maximum value of 10 or less, e.g., 5.5 to
10. Unless stated
otherwise, the expression "up to" when referring to the compositional amount
of an element
means that element is optional and includes a zero percent composition of that
particular
element. Unless stated otherwise, all compositional percentages are in weight
percent
(wt.%).
[0024] As used herein, the meaning of "a," "an," and "the" includes
singular and
plural references unless the context clearly dictates otherwise.
[0025] In the present description, aluminum alloy products and their
components may
be described in terms of their elemental composition in weight percent (wt.%).
In each alloy,
the remainder is aluminum, with a maximum wt.% of 0.15% for the sum of all
impurities.
[0026] Incidental elements, such as grain refiners and deoxidizers, or
other additives
may be present in the invention and may add other characteristics on their own
without
departing from or significantly altering the alloy described herein or the
characteristics of the
alloy described herein.
Metal strip
[0027] As discussed, the heat treatment processes of the disclosure can
be performed
on a metal strip, e.g., an aluminum alloy strip. In certain aspects, the metal
strip as described
herein can be produced from casting a metal, e.g., DC casting or continuously
casting a
metal. After casting, in certain aspects, homogenizing, hot rolling, and/or
cold rolling, and
optional annealing after hot rolling or before the final cold rolling, can be
performed to
produce the metal strip.
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[0028] In certain aspects, the metal strip can be a metal sheet, shate,
or foil. In certain
aspects, the metal strip can be a sheet. For example, in one embodiment, the
described
process is used to produce a sheet with a gauge from 0.5 mm to 4.5 mm. In some
such
aspects, the metal strip can be an aluminum alloy sheet, e.g., a heat
treatable aluminum alloy
sheet. In some aspects, the metal strip can be selected from a 2xxx series, a
6xxx series, or a
7xxx series aluminum alloy sheet. In some aspects, the metal strip is a 2xxx
series aluminum
alloy sheet. In some aspects, the metal strip is a 6xxx series aluminum alloy
sheet. In some
aspects, the metal strip is a 7xxx series aluminum alloy sheet. In certain
aspects, the metal
strip can be a shate. In some aspects, the metal strip can be an aluminum
alloy shate, e.g., a
heat treatable aluminum alloy shate. In some aspects, the metal strip can be
selected from a
2xxx series, a 6xxx series, or a 7xxx series aluminum alloy shate. In some
aspects, the metal
strip is a 2xxx series aluminum alloy shate. In some aspects, the metal strip
is a 6xxx series
aluminum alloy shate. In some aspects, the metal strip is a 7xxx series
aluminum alloy shate.
In certain aspects, the metal strip can be a foil. In some aspects, the metal
strip can be an
aluminum alloy foil, e.g., a heat treatable aluminum alloy foil. In some
aspects, the metal
strip can be selected from a 2xxx series, a 6xxx series, or a 7xxx series
aluminum alloy foil.
In some aspects, the metal strip is a 2xxx series aluminum alloy foil. In some
aspects, the
metal strip is a 6xxx series aluminum alloy foil. In some aspects, the metal
strip is a 7xxx
series aluminum alloy foil.
[0029] In certain aspects, the alloys exhibit high strength and high
deformability. . In
some cases, the alloys exhibit an increase in strength after thermal treatment
without
significant loss of deformability. The properties of the alloys are achieved
at least in part due
to the methods of processing the alloys to produce the described foils,
shates, sheets or other
products.
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[0030] In some examples, the alloys can have the following elemental
composition as
provided in Table 1.
Table 1
Element Weight Percentage (wt. %)
Cu 0.05 ¨ 1.2
Si 0.6 ¨ 1.5
Mg 0.3 ¨ 1.2
Cr 0.0 ¨ 0.25
Mn 0.0 ¨ 0.35
Fe 0.1 ¨ 0.35
Zr 0.0 ¨ 0.25
Zn 0.0 ¨ 1.0
Ti 0.0 ¨ 0.3
Ni 0.0 ¨ 0.04
0.0 ¨0.05 (each)
Impurities
0.0 ¨ 0.15 (total)
Al
[0031] In some examples, the alloys can have the following elemental
composition as
provided in Table 2.
Table 2
Element Weight Percentage (wt. %)
Cu 0.6 ¨ 1.2
Si 0.6 ¨ 1.1
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Mg 0.7 - 1.2
Cr 0.0 - 0.25
Mn 0.0 - 0.35
Fe 0.1 - 0.3
Zr 0.0 - 0.25
Zn 0.0 - 0.3
Ti 0.0 - 0.10
Ni 0.0 - 0.04
0.0 -0.05 (each)
Impurities
0.0 - 0.15 (total)
Al
In other examples, the alloys can have the following elemental composition as
provided in Table 3.
Table 3
Element Weight Percentage (wt. %)
Cu 0.7 - 1.0
Si 0.7 - 1.0
Mg 0.8 - 1.1
Cr 0.01 - 0.20
Mn 0.0 - 0.25
Fe 0.16 - 0.26
Zr 0.0 - 0.2
Zn 0.0 - 0.2
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Ti 0.01 ¨ 0.07
Ni 0.0 ¨ 0.034
0.0 ¨0.05 (each)
Impurities
0.0 ¨ 0.15 (total)
Al
[0032] In one example, an aluminum alloy can have the following elemental
composition as provided in Table 4. In certain aspects, the alloy is used to
prepare aluminum
foils and sheets.
Table 4
Element Weight Percentage (wt. %)
Cu 0.75 ¨0.9
Si 0.75 ¨0.9
Mg 0.85 ¨ 1.0
Cr 0.05 ¨ 0.18
Mn 0.05 ¨ 0.18
Fe 0.16 ¨ 0.26
Zr 0.0 ¨ 0.15
Zn 0 ¨ 0.15
Ti 0.012 ¨ 0.05
Ni 0.0 ¨ 0.034
0.0 ¨0.05 (each)
Impurities
0.0 ¨ 0.15 (total)
Al
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[0033] In certain examples, the disclosed alloy includes copper (Cu) in
an amount
from about 0.05% to about 1.2% (e.g., from about 0.1% to about 1.2%, from
about 0.2 %
to about 1.1 %, from about 0.3 % to about 1.0 %, from about 0.4 % to about 1.0
%, from
about 0.6% to about 1.1 %, from about 0.65% to about 0.9%, from about 0.7 % to
about 1.0
or from about 0.6 % to about 0.7%) based on the total weight of the alloy. For
example,
the alloys can include about 0.05%, about 0.06 %, about 0.07 %, about 0.08 %,
about 0.09
%, about 0.1 %, about 0.11%, about 0.12%, about 0.13%, about 0.14%, about
0.15%,
about 0.16 %, about 0.17%, about 0.18 %, about 0.19 %, about 0.2 %, about 0.21
%, about
0.22 %, about 0.23 %, about 0.24%, about 0.25%, about 0.26 %, about 0.27 %,
about 0.28
%, about 0.29 %, about 0.3 %, about 0.31 %, about 0.32 %, about 0.33 %, about
0.34 %,
about 0.35 %, about 0.36%, about 0.37 %, about 0.38 %, about 0.39 %, about 0.4
%, about
0.41 %, about 0.42 %, about 0.43 %, about 0.44%, about 0.45 %, about 0.46 %,
about 0.47
%, about 0.48 %, about 0.49%, about 0.5%, about 0.51 %, about 0.52%, about
0.53%,
about 0.54 %, about 0.55%, about 0.56 %, about 0.57 %, about 0.58 %, about
0.59 %, about
0.6%, about 0.61 %, about 0.62 %, about 0.63 %, about 0.64%, about 0.65%,
about 0.66 %,
about 0.67 %, about 0.68%, about 0.69%, about 0.7 %, about 0.71%, about 0.72
%, about
0.73 %, about 0.74 %, about 0.75%, about 0.76%, about 0.77 %, about 0.78 %,
about 0.79
%, about 0.8 %, about 0.81%, about 0.82%, about 0.83%, about 0.84%, about
0.85%,
about 0.86 %, about 0.87%, about 0.88%, about 0.89 %, about 0.9 %, about 0.91
%, about
0.92 %, about 0.93 %, about 0.94%, about 0.95%, about 0.96 %, about 0.97 %,
about 0.98
%, about 0.99 %, about 1.0%, about 1.01 %, about 1.02%, about 1.03 %, about
1.04%,
about 1.05%, about 1.06%, about 1.07%, about 1.08%, about 1.09%, about or
about 1.1%
Cu. All expressed in wt. %.
[0034] In certain examples, the disclosed alloy includes silicon (Si) in
an amount
from about 0.6 % to about 1.5 % (e.g., from about 0.7 % to about 1.3 %, from
about 0.8 % to
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about 1.2 %, from about 0.9% to about 1.1 %, from about 0.6 % to about 0.9%,
from about
0.9% to about 1.1 %, or from about 1.0% to about 1.1 %) based on the total
weight of the
alloy. For example, the alloys can include about 0.6%, about 0.61%, about 0.62
%, about
0.63 %, about 0.64 %, about 0.65%, about 0.66%, about 0.67 %, about 0.68 %,
about 0.69
%, about 0.7 %, about 0.71 %, about 0.72 %, about 0.73 %, about 0.74 %, about
0.75 %,
about 0.76 %, about 0.77%, about 0.78 %, about 0.79 %, about 0.8 %, about 0.81
%, about
0.82 %, about 0.83 %, about 0.84%, about 0.85%, about 0.86 %, about 0.87 %, ab
out 0.88
%, about 0.89 %, about 0.9 %, about 0.91 %, about 0.92 %, about 0.93 %, about
0.94 %,
about 0.95 %, about 0.96%, about 0.97 %, about 0.98 %, about 0.99 %, about 1.0
%, about
1.01 %, about 1.02 %, about 1.03 %, about 1.04%, about 1.05 %, about 1.06 %,
about 1.07
%, about 1.08 %, about 1.09%, or about 1.1% Si. All expressed in wt. %.
[0035] In certain examples, the disclosed alloy includes magnesium (Mg)
in an
amount from about 0.3 % to about 1.3 % (e.g., from about 0.4 % to about 1.25
%, from about
0.5 % to about 1.2 %, from about 0.7 % to about 1.1 %, from about 0.8 % to
about 1.25%,
from about 1.1 % to about 1.25%, from about 1.1 % to about 1.2 %, from about
1.0% to
about 1.2 %, from about 1.05 % to about 1.3 %, or from about 1.15% to about
1.3 %) based
on the total weight of the alloy. For example, the alloys can include about
0.3 %, about 0.4 %,
about 0.5 %, about 0.6%, about 0.7 %, about 0.71 %, about 0.72%, about 0.73 %,
about 0.74
%, about 0.75 %, about 0.76 %, about 0.77 %, about 0.78 %, about 0.79 %, about
0.8 %,
about 0.81 %, about 0.82%, about 0.83 %, about 0.84 %, about 0.85 %, about
0.86 %, about
0.87 %, about 0.88 %, about 0.89 %, about 0.9 %, about 0.91%, about 0.92%,
about 0.93 %,
about 0.94 %, about 0.95%, about 0.96 %, about 0.97 %, about 0.98 %, about
0.99 %, about
1.0%, about 1.01 %, about 1.02 %, about 1.03 %, about 1.04%, about 1.05%,
about 1.06 %,
about 1.07 %, about 1.08%, about 1.09 %, about 1.1 %, about 1.11%, about 1.12
%, about
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1.13%, about 1.14%, about 1.15%, about 1.16%, about 1.17 %, about 1.18%, about
1.19
%, or about 1.2 % Mg. All expressed in wt. %.
[0036] In certain aspects, the alloy includes chromium (Cr) in an amount
up to about
0.25 % (e.g., from about 0 % to about 0.25 %, from about 0.03 % to about 0.06
%, from
about 0.03 % to about 0.19 %, or from about 0.06 % to about 0.1 %) based on
the total
weight of the alloy. For example, the alloy can include about 0.001 %, about
0.002 %, about
0.003%, about 0.004 %, about 0.005 %, about 0.006%, about 0.007%, about 0.008
%, about
0.059%, about 0.01 %, about 0.011%, about 0.012 %, about 0.013 %, about 0.014
%, about
0.015%, about 0.016%, about 0.017 %, about 0.018%, about 0.019%, about 0.02 %,
about
0.021%, about 0.022 %, about 0.023 %, about 0.024 %, about 0.025 %, about
0.026 %, about
0.027%, about 0.028 %, about 0.029 %, about 0.03 %, about 0.031 %, about 0.032
%, about
0.033%, about 0.034 %, about 0.035 %, about 0.036%, about 0.037%, about 0.038
%, about
0.039%, about 0.04 %, about 0.041%, about 0.042 %, about 0.043 %, about 0.044
%, about
0.045%, about 0.046 %, about 0.047 %, about 0.048%, about 0.049%, about 0.05
%, about
0.051%, about 0.052 %, about 0.053 %, about 0.054 %, about 0.055 %, about
0.056 %, about
0.057 %, about 0.058 %, about 0.059 %, about 0.06 %, about 0.061 %, about
0.062 %, ab out
0.063%, about 0.064 %, about 0.065 %, about 0.066 %, about 0.067%, about 0.068
%, about
0.069%, about 0.07 %, about 0.071%, about 0.072 %, about 0.073 %, about 0.074
%, about
0.075%, about 0.076 %, about 0.077 %, about 0.078%, about 0.079%, about 0.08
%, about
0.081 %, about 0.082 %, about 0.083 %, about 0.084 %, about 0.085 %, about
0.086 %, about
0.087 %, about 0.088 %, about 0.089 %, about 0.09 %, about 0.091 %, about
0.092 %, ab out
0.093%, about 0.094 %, about 0.095 %, about 0.096%, about 0.097%, about 0.098
%, about
0.099 %, about 0.1 %, about 0.11%, about 0.12%, about 0.13 %, about 0.14 %,
about 0.15
%, about 0.16 %, about 0.17%, about 0.18%, about 0.19%, about 0.2%, about 0.21
%,
about 0.22 %, about 0.23 %, about 0.24 %, or about 0.25 % Cr. All expressed in
wt. %. In
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some cases, Cr is not present in the alloy (i.e., 0 %). In some examples, Cr
can control grain
structure and prevent grain growth and recrystallization. Higher amounts of Cr
can provide a
higher formability and improved b endability in aged temper.
[0037] In certain examples, the alloy can include manganese (Mn) in an
amount up to
about 0.35 % (e.g., from about 0 % to about 0.35 %, from about 0.05 % to about
0.18 %,
from about 0.1 % to about 0.35 %, or from about 0.1% to about 0.3 %) b ased on
the total
weight of the alloy. For example, the alloy can include about 0.001 %, about
0.002 %, about
0.003%, about 0.004 %, about 0.005 %, about 0.006%, about 0.007%, about 0.008
%, about
0.059%, about 0.01 %, about 0.011%, about 0.012 %, about 0.013 %, about 0.014
%, about
0.015%, about 0.016%, about 0.017 %, about 0.018%, about 0.019%, about 0.02 %,
about
0.021%, about 0.022 %, about 0.023 %, about 0.024 %, about 0.025 %, about
0.026 %, about
0.027%, about 0.028%, about 0.029 %, about 0.03 %, about 0.031 %, about 0.032
%, about
0.033%, about 0.034 %, about 0.035 %, about 0.036%, about 0.037%, about 0.038
%, about
0.039%, about 0.04 %, about 0.041%, about 0.042 %, about 0.043 %, about 0.044
%, about
0.045%, about 0.046%, about 0.047 %, about 0.048%, about 0.049%, about 0.05 %,
about
0.051%, about 0.052 %, about 0.053 %, about 0.054 %, about 0.055 %, about
0.056 %, about
0.057%, about 0.058%, about 0.059 %, about 0.06 %, about 0.061 %, about 0.062
%, about
0.063%, about 0.064 %, about 0.065 %, about 0.066%, about 0.067%, about 0.068
%, about
0.069%, about 0.07 %, about 0.071%, about 0.072 %, about 0.073 %, about 0.074
%, about
0.075%, about 0.076%, about 0.077 %, about 0.078%, about 0.079%, about 0.08 %,
about
0.081%, about 0.082 %, about 0.083 %, about 0.084 %, about 0.085 %, about
0.086 %, about
0.087%, about 0.088%, about 0.089 %, about 0.09 %, about 0.091 %, about 0.092
%, about
0.093%, about 0.094 %, about 0.095 %, about 0.096%, about 0.097%, about 0.098
%, about
0.099 %, about 0.1%, about 0.11%, about 0.12 %, about 0.13 %, about 0.14 %,
about 0.15
%, about 0.16 %, about 0.17%, about 0.18%, about 0.19%, about 0.2%, about 0.21
%,
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about 0.22%, about 0.23%, about 0.24 %, about 0.25%, about 0.26%, about 0.27%,
about
0.28%, about 0.29 %, about 0.3 %, about 0.31 %, about 0.32 %, about 0.33 %,
about 0.34 %,
or about 0.35% Mn. In some cases, Mn is not present in the alloy (i.e., 0%).
All expressed in
wt. %.
[0038] In certain aspects, the alloy also includes iron (Fe) in an amount
from about
0.1 % to about 0.35 % (e.g., from about 0.1 % to about 0.3 %, from about 0.1 %
to about 0.25
%, from about 0.18 % to about 0.25%, from about 0.2 % to about 0.21%, or from
about 0.15
% to about 0.22 %) based on the total weight of the alloy. For example, the
alloy can include
about 0.1 %, about 0.11 %, about 0.12 %, about 0.13 %, about 0.14%, about 0.15
%, about
0.16%, about 0.17%, about 0.18%, about 0.19%, about 0.2 %, about 0.21%, about
0.22 %,
about 0.23 %, about 0.24 %, about 0.25 %, about 0.26 %, about 0.27 %, about
0.28 %, about
0.29 %, or about 0.30 % Fe. In some cases, Fe is not present in the alloy
(i.e., 0 %). All
expressed in wt. %.
[0039] In certain aspects, the alloy includes zirconium (Zr) in an amount
up to about
0.25 % (e.g., from about 0 % to about 0.2 %, from about 0.01 % to about 0.25
%, from about
0.01 % to about 0.15 %, from about 0.01 % to about 0.1 %, or from about 0.02 %
to about
0.09 %) based on the total weight of the alloy. For example, the alloy can
include about 0.001
%, about 0.002%, about 0.003%, about 0.004 %, about 0.005 %, about 0.006%,
about 0.007
%, about 0.008 %, about 0.009%, about 0.01%, about 0.02 %, about 0.03 %, about
0.04 %,
about 0.05 %, about 0.06%, about 0.07 %, about 0.08 %, about 0.09 %, about 0.1
%, about
0.11%, about 0.12%, about 0.13 %, about 0.14 %, about 0.15 %, about 0.16 %,
about 0.17
%, about 0.18 %, about 0.19%, about 0.2%, about 0.21 %, about 0.22%, about
0.23%,
about 0.24 %, or about 0.25 Zr. In certain aspects, Zr is not present in the
alloy (i.e., 0 %).
All expressed in wt. %. In some examples, Zr can control grain structure and
prevent grain
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growth and recrystallization. Higher amounts of Zr can provide a higher
formability and
improved bendability as well in T4 and aged temper.
[0040] In certain aspects, the alloy described herein includes zinc (Zn)
in an amount
up to about 1.0% (e.g., from about 0% to about 1.0%, from about 0.001% to
about 0.3 %,
from about 0.005 % to about 0.09%, from about 0.004 % to about 0.3 %, from
about 0.03 %
to about 0.2%, or from about 0.06% to about 0.1 %)based on the total weight of
the alloy.
For example, the alloy can include about 0.001 %, about 0.002 %, about 0.003
%, about
0.004 %, about 0.005%, about 0.006 %, about 0.007%, about 0.008%, about
0.009%, about
0.01%, about 0.011 %, about 0.012%, about 0.013 %, about 0.014 %, about 0.015
%, about
0.016%, about 0.017 %, about 0.018 %, about 0.019%, about 0.02 %, about 0.021
%, about
0.022 %, about 0.023 %, about 0.024%, about 0.025%, about 0.026%, about 0.027
%, about
0.028 %, about 0.029%, about 0.03%, about 0.04%, about 0.05 %, about 0.06 %,
about 0.07
%, about 0.08 %, about 0.09%, about 0.1 %, about 0.11 %, about 0.12%, about
0.13%,
about 0.14 %, about 0.15%, about 0.16 %, about 0.17 %, about 0.18 %, about
0.19 %, about
0.2%, about 0.21 %, about 0.22 %, about 0.23 %, about 0.24%, about 0.25%,
about 0.26 %,
about 0.27 %, about 0.28%, about 0.29 %, about 0.3 %, about 0.31%, about 0.32
%, about
0.33 %, about 0.34 %, about 0.35 %, about 0.36%, about 0.37 %, about 0.38 %,
about 0.39
%, about 0.4 %, about 0.41 %, about 0.42 %, about 0.43 %, about 0.44 %, about
0.45 %,
about 0.46 %, about 0.47%, about 0.48 %, about 0.49 %, about 0.50 %, about
0.51 %, ab out
0.52 %, about 0.53 %, about 0.54%, about 0.55%, about 0.56 %, about 0.57 %,
about 0.58
%, about 0.59 %, about 0.6 %, about 0.61 %, about 0.62 %, about 0.63 %, about
0.64 %,
about 0.65 %, about 0.66%, about 0.67 %, about 0.68 %, about 0.69 %, about 0.7
%, about
0.71 %, about 0.72 %, about 0.73 %, about 0.74%, about 0.75 %, about 0.76 %,
about 0.77
%, about 0.78 %, about 0.79%, about 0.8%, about 0.81 %, about 0.82%, about
0.83%,
about 0.84 %, about 0.85%, about 0.86 %, about 0.87 %, about 0.88 %, about
0.89 %, ab out
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0.90 %, about 0.91 %, about 0.92%, about 0.93 %, about 0.94 %, about 0.95 %,
about 0.96
%, about 0.97 %, about 0.98%, about 0.99%, or about 1.0% Zn. In some cases, Zn
is not
present in the alloy (i.e., 0 %). All expressed in wt. %. In certain aspects,
Zn can benefit
forming, including bending and the reduction of bending anisotropy in foil,
sheet, and s h ate
products.
[0041] In certain aspects, the alloy includes titanium (Ti) in an amount
of up to about
0.3 % (e.g., from about 0% to about 0.3 %, from about 0.01 % to about 0.25%,
from about
0.05 % to about 0.2 %, or up to about 0.1 %) based on the total weight of the
alloy. For
example, the alloy can include about 0.01 %, about 0.011 %, about 0.012%,
about 0.013 %,
about 0.014 %, about 0.015 %, about 0.016 %, about 0.017 %, about 0.018 %,
about 0.019 %,
about 0.02 %, about 0.025 %, about 0.03 %, about 0.035 %, about 0.04 %, about
0.045 %,
about 0.05%, about 0.055 %,0.06%, about 0.065%, about 0.07%, about 0.075 %,
about
0.08 %, about 0.085 %, about 0.09 %, about 0.095%, about 0.1 %, about 0.11 %,
about 0.12
%, about 0.13 %, about 0.14 %, about 0.15 %, about 0.16 %, about 0.17 %, about
0.18 %,
about 0.19 %, about 0.2 %, about 0.21 %, about 0.22%, about 0.23 %, about 0.24
%, about
0.25 %, about 0.26 %, about 0.27 %, about 0.28 %, about 0.29 %, or about 0.3 %
Ti. In
certain aspects, Ti is not present in the alloy (i.e., 0 %). All expressed in
wt. %.
[0042] In certain aspects, the alloy includes nickel (Ni) in an amount up
to about 0.04
% (e.g., from 0 % to about 0.02 %, from about 0.01 % to about 0.03 %, from
about 0.03 % to
about 0.04 %) based on the total weight of the alloy. For example, the alloy
can include about
0.001 %, about 0.005 %, about 0.01 %, about 0.011 %, about 0.012 %, about
0.013 %, about
0.014 %, about 0.015 %, about 0.016 %, about 0.017%, about 0.018 %, about
0.019 %, about
0.02%, about 0.021 %, about 0.022%, about 0.023 %, about 0.024 %, about 0.025
%, about
0.026%, about 0.027%, about 0.028 %, about 0.029%, about 0.03 %, about 0.031%,
about
0.032 %, about 0.033 %, about 0.034 %, about 0.035 %, about 0.036%, about
0.037 %, about
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0.038%, about 0.039 %, or about 0.04 % Ni. In certain aspects, Ni is not
present in the alloy
(i.e., 0 %). All expressed in wt. %.
[0043] Optionally, the alloy compositions can further include other minor
elements,
sometimes referred to as impurities, in amounts of about 0.05 % or below,
about 0.04 % or
below, about 0.03% or below, about 0.02% or below, or about 0.01% or below
each. These
impurities may include, but are not limited to, V, Ga, Ca, Hf, Sr, Sc, Sn, or
combinations
thereof. Accordingly, V, Ga, Ca, Hf, Sr, Sc, or Sn may be present in an alloy
in amounts of
about 0.05 % or below, about 0.04 % or below, about 0.03 % or below, about
0.02 % or
below, or about 0.01 % or below. In certain aspects, the sum of all impurities
does not exceed
about 0.15 % (e.g., 0.1 %). All expressed in wt. %. In certain aspects, the
remaining
percentage of the alloy is aluminum.
Continuous Heat Treatment Process
[0044] Certain aspects and features of the present disclosure relate to a
continuous
heat treatment process, where a metal strip is solutionized, rapidly cooled,
thermally spiked at
an elevated temperature (for example, at a temperature ranging from 120 C to
300 C), and
coiled, as described below. In certain embodiments, the metal strip is a heat
treatable alloy,
for example, a heat treatable aluminum alloy. In certain embodiments, the
thermally spiked
metal strip is cooled before or after coiling. In certain embodiments, the
thermally spiked
metal strip is only naturally cooled before or after coiling. In some
embodiments, the coil can
be cooled (e.g, using a cooling fan(s)) after coiling at the end of the
continuous heat treatment
process. In certain embodiments, the metal strip itself can be prepared from
scalping,
homogenizing, hot rolling, optionally batch annealing, and cold rolling a cast
ingot.
[0045] The continuous heat treatment process can be operated at a
specific line speed.
For example, the continuous heat treatment process can be operated at a line
speed greater
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than 5 meters/min, e.g., greater than 10 meters/min, greater than 20
meters/min, greater than
25 meters/min, greater than 30 meters/min, greater than 40 meters/min, greater
than 50
meters/min, greater than 60 meters/min, greater than 70 meters/min, greater
than 80
meters/min, greater than 90 meters/min, greater than 100 meters/min, from 10
meters/min to
100 meters/min, from 20 meters/min to 80 meters/min, from 30 meters/min to 70
meters/min,
or from 40 meters/min to 60 meters/min.
Solutionizing
[0046] Solutionizing can put into solution (e.g., aluminum solid
solution) the desired
amount of alloying elements that are present in a particular alloy. In some
aspects, the
solutionizing step can comprise heating the metal strip (e.g., plate, shate,
sheet, or foil) from
room temperature to a temperature of from about 400 C to about 590 C (e.g.,
from about
450 C to about 575 C, from about 400 C to about 525 C, from about 450 C
to about 510
C, from about 520 C to about 590 C, from about 520 C to about 580 C, from
about 520
C to about 560 C, from about 530 C to about 570 C, from about 545 C to
about 575 C,
from about 550 C to about 570 C, from about 555 C to about 565 C, from
about 540 C to
about 560 C, from about 540 C to about 575 C, from about 560 C to about
580 C, from
about 550 C to about 575 C, about 540 C, about 550 C, about 560 C, or
about 570 C).
[0047] In certain embodiments, the strip can soak at the temperature for
a period of
time. In certain aspects, the strip is allowed to soak for a time (e.g., up to
approximately 5
minutes, from about 10 seconds to about 5 minutes inclusively, from about 1
second to about
3 minutes, or from about 5 seconds to about 5 minutes). For example, the strip
can be soaked
at the temperature (e.g., from about 525 C to about 590 C) for less than 20
seconds, less
than 25 seconds, less than 30 seconds, less than 35 seconds, less than 40
seconds, less than 45
seconds, less than 50 seconds, less than 55 seconds, less than 60 seconds,
less than 65
seconds, less than 70 seconds, less than 75 seconds, less than 80 seconds,
less than 85
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seconds, less than 90 seconds, less than 95 seconds, less than 100 seconds,
less than 105
seconds, less than 110 seconds, less than 115 seconds, less than 120 seconds,
less than 125
seconds, less than 130 seconds, less than 135 seconds, less than 140 seconds,
less than 145
seconds, or less than 150 seconds, or less than 5 minutes, or anywhere in
between.
[0048] In certain aspects, the solutionizing can be carried out in a
continuous process,
e.g., a continuous heat treatment line. In some embodiments, the continuous
process (e.g.,
continuous heat treatment line) can have a specific line speed.
[0049] In certain aspects, the solutionizing step is performed on a metal
strip
immediately after a hot rolling step and/or a cold rolling step. In other
aspects, the
solutionizing step is performed on a metal strip after (e.g., >48 hour after)
a hot rolling step
and/or a cold rolling step. In certain aspects, the solutionizing step is
performed after an
annealing and cold rolling step.
Rapid Cooling
[0050] Without being bound by theory, in order to lock the solute
elements and.
excess vacancies into the metal (e.g., aluminum) matrix of the metal strip,
the metal strip can
be cooled very rapidly. Thus, in some aspects, after solutionizing, the metal
strip can be
rapidly cooled to reduce the temperature of the metal strip. In some aspects,
the transfer time
from the solutionizing furnace into the cooling medium is very short (e.g.,
less than I s, less
than 2 s, less than 3 s, less than 5 s, less than 10 s, less than 15 s, less
than 20 s, less than 25 s,
less than 30 s, less than 35 s, less than 40 s, less than 45 s, less than 50
s, less than 55 s, less
than I min, less than 2 min, less than 3 min, less than 4 min, less than 5
min, or less than 10
min). The time for transfer of the solutionized metal begins from the moment
.that the furnace
door begins to open and goes to the point at which the aluminum alloy is
completely
immersed and submerged. If the transfer time exceeds the prescribed time
limit, incomp I ete
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solutionizing can occur, which means nonuniform metallurgical and mechanical
conditions of
the particular alloy.
[0051] In certain aspects, after solutionizing, the metal strip can be
cooled at a rate
that can vary between about 1 C/s to 400 C/s in a rapid cooling step that is
based on the
selected gauge. For example, the rapid cooling rate can be from about 50 C/s
to about 3 75
C/s, from about 60 C/s to about 375 C/s, from about 70 C/s to about 350
C/s, from about
80 C/s to about 325 C/s, from about 90 C/s to about 300 C/s, from about
100 C/s to
about 275 C/s, from about 125 C/s to about 250 C/s, from about 150 C/s to
about 225
C/s, from about 175 C/s to about 200 C/s, from about 10 C/s to about 125
C/s, or from
about 20 C/s to about 125 C/s. In some aspects, the metal strip can be
rapidly cooled to a
temperature of less than 100 C, e.g., less than 90 C, less than 80 C, less
than 70 C, less
than 60 C, less than 50 C, less than 45 C, less than 40 C, less than 35 C,
less than 30 C,
less than 25 C, less than 20 C, less than 15 C, from about 20 C to about
80 C, from about
20 C to about 70 C , from about 20 C to about 60 C, from about 25 C to
about 5 0 C,
from about 25 C to about 40 C, to about 20 C, to about 25 C, to about 30
C, to about 35
C, to about 40 C, to about 45 C, or to about 50 C.
[0052] In certain aspects, the metal strip can be rapidly cooled with a
liquid (e.g.,
water) and/or a gas or another selected cooling medium. In certain aspects,
the metal strip is
rapidly cooled with air. In certain aspects, the metal strip can be rapidly
cooled with water.
Thermal spiking
[0053] The metal strip can be subjected to a thermal spike treatment at
elevated
temperature. As described herein, using thermal spike temperatures higher than
those
previously disclosed in the art helped achieve the unexpected benefits of the
present
disclosure. In some aspects, the thermal spike temperature (i.e., the peak
temperature that the
metal strip is exposed to, not necessarily the temperature of the metal strip
itself) is in the
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range of from about 100 C to about 300 C, e.g., from about 120 C to about
300 C, from
about 150 C to about 300 C, from about 170 C to about 280 C, from about
180 C to
about 270 C, from about 190 C to about 260 C, from about 200 C to about
250 C, from
about 210 C to about 250 C, from about 220 C to about 250 C, from about
220 C to
about 240 C, about 200 C, about 210 C, about 220 C, about 230 C, about
240 C, or
about 250 C. In some aspects, the metal strip itself reaches to within 100 C
of the thermal
spike temperature, e.g., within 90 C, within 80 C, within 70 C, within 60
C, within 50 C,
within 40 C, within 30 C, within 20 C, within 10 C, within 5 C, or within
1 C.
[0054] In some aspects, the thermal spike treatment occurs after
solutionizing and air
cooling the metal strip. In some aspects, the thermal spike treatment can
occur at the same
processing line speed as the solutionizing and rapid cooling, e.g., as part of
a continuous heat
treatment process.
[0055] Conventional 6XXX materials in T4 or T4P tempers contain large
number of
fine metastable clusters and zones uniformly distributed throughout a metal
matrix. In the
conventional process, during the paint cure, some fine unstable clusters/zones
re-dissolve in
the metal matrix, while other improve the material strength due to age
hardening. The process
described herein allows the alloy material to exhibit an enhanced aging
response (hardness
response). Without being bound by theory, it is believed that thermal spiking
between 150
and 320 C, (for example, in a long reheater furnace) e.g., between about 150
and 300 C,
between about 180 and 300 C, or between about 150 and 225 C, followed by
coiling and
coil cooling forms some of the clusters and zones and enhances the
precipitation process
during coil cooling.
[0056] The period of time for which the temperature is maintained at the
peak thermal
spike temperature may range from zero to any time that is practical in the
circumstances. In
some aspects, the thermal spike treatment occurs at the speed of the
processing line of the
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continuous heat treatment process (for example in a long furnace). For
example, the speed of
the processing line and the speed of the thermal spike treatment can occur at
a speed of from
about 1 meter/min to about 120 meters/min, e.g., from about 2 meters/min to
about 110
meters/min, from about 5 meters/min to about 100 meters/min, from about 10
meters/min to
about 600 meters/min, from about 20 meters/min to about 500 meters/min, from
about 25
meters/min to about 500 meters/min, from about 30 meters/min to about 400
meters/min,
from about 40 meters/min to about 350 meters/min, from about 50 meters/min to
about 300
meters/min, or from about 100 meters/min to about 250 meters/min. In practice,
the period is
usually from zero up to about 5 minutes, e.g., from about 1 sec to about 5
min, from about 2
sec to about 4 min, from about 3 sec to about 3 min, from about 5 sec to about
2 min, from
about 7 sec to about 1 min, or from about 10 sec to about 30 sec.
[0057] In some aspects, the thermal spike treatment is carried out at a
heating rate of
(i.e., the temperature of the metal strip increases at a rate) about 1 C/min
to about 50 C/s
(e.g., from about 1 C/s to about 40 C/s, from about 2 C/s to about 40 C/s,
from about 3
C/s to about 35 C/s, from about 3 C/s to about 30 C/s, from about 5 C/s to
about 30 C/s,
from about 10 C/s to about 25 C/s, or from about 2 C/s to about 10 C/s).
[0058] In some aspects, the thermal spike treatment is performed in a
reheater
furnace, e.g., a continuous reheater furnace. In some aspects, the thermal
spike treatment is
performed in a long reheater furnace. For example, the furnace can have an
effective length
of (i.e., a length that the metal strip is heated in a continuous process) of
at least 10 meters,
e.g., at least 20 meters, at least 25 meters, at least 30 meters, at least 40
meters, at least 50
meters, at least 60 meters, at least 70 meters, at least 80 meters, at least
90 meters, or at least
100 meters. Without limiting the disclosure, this may allow for an increased
line speed
and/or thermal spike time.
Aging
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[0059] In some aspects, the metal strip does not undergo an aging
process. In some
aspects, the thermal spike of the metal strip in combination with coiling of
the metal strip
and/or cooling of the metal strip can take the place of age hardening.
Cooling
[0060] In some aspects, the metal strip can be cooled after the thermal
spike
treatment. In some aspects, this cooling can occur after coiling. In other
aspects, this cooling
can occur before coiling. And in some aspects, cooling can occur before and/or
after coiling.
For example, in some aspects, the metal strip can be air cooled, e.g., using
at least one fan. In
some aspects, the metal strip is only naturally cooled (for example, during
the passage of the
strip between the thermal spike treatment and coiling), meaning that there is
no apparatus or
process used to cool the metal strip prior to coiling. For example, the metal
strip might only
be exposed to the ambient conditions (e.g., at the line speed of the
continuous heat treatment
process) prior to coiling. In some aspects, the metal strip is only naturally
cooled after
coiling. As described herein, naturally cooling (e.g. only exposure to the
ambient conditions
prior to cooling) does not fall within the term "cooling" or "cooled" as used
previously in the
art. In some aspects, the cooling or natural cooling can be carried out until
the metal strip
reaches ambient temperature.
[0061] In some aspects, the metal strip and/or the coiled metal strip can
be cooled or
naturally cooled at a rate of less than or equal to about 60 C/hour (e.g.,
less than or equal to
about 50 C/hour, less than or equal to about 40 C/hour, less than or equal
to about 30
C/hour, less than or equal to about 20 C/hour, less than or equal to about 10
C/hour, less
than or equal to about 5 C/hour, less than or equal to about 3 C/hour, less
than or equal to
about 2.5 C/hour, less than or equal to about 2 C/hour, less than or equal
to about 1.5
C/hour, less than or equal to about 1 C/hour, or less than or equal to about
0.8 C/hour).
Methods of Preparing the Metal Strip
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[0062] In certain aspects, the disclosed metal (e.g., alloy) strip
compositions are
products of disclosed methods. Without limiting the disclosure, alloy
properties, such as
aluminum alloy properties, are partially determined by the formation of
microstructures
during the alloy's preparation. In certain aspects, the method of preparation
for an alloy
composition may influence or even determine whether the alloy will have
properties adequate
for a desired application.
[0063] The metal (e.g., alloy) strip described herein can be cast into
ingots using a
casting method. For example, the casting process can comprise a Direct Chill
(DC) casting
process. In another example, the casting process can comprise a continuous
casting process.
The cast ingot can then be subjected to further processing steps. In one non-
limiting
example, the processing method includes scalping, homogenization, hot rolling,
optional
batch annealing, and cold rolling, prior to the aforementioned solutionizing,
rapid cooling,
thermal spike treatment, and coiling and subsequent cooling (e.g., fan cooling
after coiling).
Homogenization
[0064] In some aspects, the homogenization step can involve a one-step
homogenization or a two-step homogenization. In one example of the
homogenization step, a
one-step homogenization is performed where an ingot prepared from an alloy
composition
described herein is heated to attain a peak metal temperature (PMT) of about,
or at least
about, 500 C (e.g., at least 520 C, at least 530 C, at least 540 C, at least
550 C, at least
560 C, at least 570 C, or at least 580 C). For example, the ingot can be
heated to a
temperature of from about 520 C to about 580 C, from about 530 C to about
575 C, from
about 535 C to about 570 C, from about 540 C to about 565 C, from about
545 C to
about 560 C, from about 530 C to about 560 C, or from about 550 C to about
580 C . In
some cases, the heating rate to the peak metal temperature can be about 100
C/hour or less,
75 C/hour or less, 50 C/hour or less, 40 C/hour or less, 30 C/hour or
less, 25 C/hour or
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less, 20 C/hour or less, 15 C/hour or less, or 10 C/hour or less. In other
cases, the heating
rate to the peak metal temperature can be from about 10 C/min to about 100
C/m in (e.g.,
about 10 C/min to about 90 C/min, about 10 C/min to about 70 C/min, about
10 C/min
to about 60 C/min, from about 20 C/min to about 90 C/min, from about 30
C/min to
about 80 C/min, from about 40 C/min to about 70 C/min, or from about 50
C/min to
about 60 C/min).
[0065] The ingot is then allowed to soak (i.e., held at the indicated
temperature) for a
period of time. According to one non-limiting example, the ingot is allowed to
soak for up to
about 8 hours (e.g., from about 5 seconds to 8 hours, or from about 30 minutes
to about 8
hours, inclusively). For example, the ingot can be soaked at a temperature of
at least 500 C
for 30 minutes, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours,
8 hours, or
anywhere in between.
[0066] In another example of the homogenization step, a two-step
homogenization is
performed where an ingot prepared from an alloy composition described herein
is heated to
attain a first temperature of about, or at least about, 480 C to about 520
C. For example, the
ingot can be heated to a first temperature of about 480 C, 490 C, 500 C, 510
C, or 520 C.
In certain aspects, the heating rate to the first temperature can be from
about 10 C/min to
about 100 C/min (e.g., about 10 C/min to about 90 C/min, about 10 C/min to
about 70
C/min, about 10 C/min to about 60 C/min, from about 20 C/min to about 90
C/min, from
about 30 C/min to about 80 C/min, from about 40 C/min to about 70 C/min,
or from
about 50 C/min to about 60 C/min). In other aspects, the heating rate to the
first
temperature can be from about 10 C/hour to about 100 C/hour (e.g., about 10
C/ hour to
about 90 C/ hour, about 10 C/ hour to about 70 C/ hour, about 10 C/ hour
to about 60 C/
hour, from about 20 C/ hour to about 90 C/ hour, from about 30 C/ hour to
about 80 C/
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hour, from about 40 C/ hour to about 70 C/hour, or from about 50 C/ hour to
about 60 C/
hour).
[0067] The ingot is then allowed to soak for a period of time. In certain
cases, the
ingot is allowed to soak for up to about 6 hours (e.g., from 5 seconds to 6
hours, or from 30
minutes to 6 hours, inclusively). For example, the ingot can be soaked at a
temperature of
from about 480 C to about 520 C for 30 minutes, 1 hour, 2 hours, 3 hours, 4
hours, 5 hours,
or 6 hours, or anywhere in between.
[0068] In the second step of the two-step homogenization process, the
ingot can be
further heated from the first temperature to a second temperature of greater
than about 520 C
(e.g., greater than 520 C, greater than 530 C, greater than 540 C, greater
than 550 C,
greater than 560 C, greater than 570 C, or greater than 580 C). For
example, the ingot can
be heated to a second temperature of from about 520 C to about 580 C, from
about 530 C
to about 575 C, from about 535 C to about 570 C, from about 540 C to about
565 C,
from about 545 C to about 560 C, from about 530 C to about 560 C, or from
about 550
C to about 580 C. The heating rate to the second temperature can be from
about 10 C/min
to about 100 C/min (e.g., from about 20 C/min to about 90 C/min, from about
30 C/min
to about 80 C/min, from about 10 C/min to about 90 C/min, from about 10
C/min to
about 70 C/min, from about 10 C/min to about 60 C/min, from about 40 C/min
to about
70 C/min, or from about 50 C/min to about 60 C/min).
[0069] In other aspects, the heating rate to the second temperature can
be from about
C/hour to about 100 C/hour (e.g., from about 10 C/ hour to about 90 C/
hour, from
about 10 C/ hour to about 70 C/hour, from about 10 C/ hour to about 60 C/
hour, from
about 20 C/ hour to about 90 C/hour, from about 30 C/ hour to about 80 C/
hour, from
about 40 C/ hour to about 70 C/hour, or from about 50 C/ hour to about 60
C/hour).
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[0070] The ingot is then allowed to soak for a period of time. In certain
cases, the
ingot is allowed to soak for up to about 6 hours (e.g., from 5 seconds to 6
hours, or from 30
minutes to 6 hours, inclusively). For example, the ingot can be soaked at a
temperature of
from about 520 C to about 580 C for 30 minutes, 1 hour, 2 hours, 3 hours, 4
hours, 5 hours,
or 6 hours, or anywhere in between.
Hot Rolling
[0071] In some aspects, following the homogenization step, a hot rolling
step can be
performed. In certain cases, the ingots are laid down and hot-rolled with an
entry
temperature range of about 380 C to about 540 C. For example, the entry
temperature can
be, for example, about 505 C, 510 C, 515 C, 520 C, 525 C, 530 C, 535 C,
or 540 C.
In certain cases, the hot roll exit temperature can range from about 230 C to
about 420 C
(e.g., from about 330 C to about 370 C). For example, the hot roll exit
temperature can be
about 255 C, 260 C, 265 C, 270 C, 275 C, 280 C, 285 C, 290 C, 295 C,
300 C, 305
C, 310 C, 315 C, 320 C, 325 C, 330 C, 335 C, 340 C, 345 C, 350 C, 355
C, 360
C, 365 C, 370 C, 375 C, or 380 C and can be combined with any of the above
entry
temperatures.
[0072] In certain cases, the ingot can be hot rolled to an about 2 mm to
about 15 mm
thick gauge (e.g., from about 5 mm to about 12 mm thick gauge), which is
referred to as a
shate. For example, the ingot can be hot rolled to an about 4 mm thick gauge,
about 5 mm
thick gauge, about 6 mm thick gauge, about 7 mm thick gauge, about 8 mm thick
gauge,
about 9 mm thick gauge, about 10 mm thick gauge, about 11 mm thick gauge,
about 12 mm
thick gauge, about 13 mm thick gauge, about 14 mm thick gauge, or about 15 mm
thick
gauge. In certain cases, the ingot can be hot rolled to a gauge greater than
15 mm thick (i.e.,
a plate). In other cases, the ingot can be hot rolled to a gauge less than 4
mm (i.e., a sheet).
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The hot rolled coil can be batch annealed in some cases before cold rolling in
some aspects. It
is also possible in certain embodiments that the annealing is carried out
after a first cold pass
or a second cold pass, before the final cold pass.
Cold Rolling
[0073] In some aspects, a cold rolling step can be performed following
the hot rolling
step. In certain aspects, the rolled product from the hot rolling step can be
cold rolled to a
sheet (e.g., below approximately 4.0 mm). In certain aspects, the rolled
product is cold rolled
to a thickness of 0.6 mm to 1.0 mm, 1.0 mm to 3.0 mm, or 3.0 mm to 4.0 mm. In
certain
aspects, the alloy is cold rolled to about 3.5 mm or less, 3 mm or less, 2.5
mm or less, 2 mm
or less, 1.5 mm or less, or 1 mm or less. For example, the rolled product can
be cold rolled to
about 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm,
1.5
mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2.0 mm, 2.1 mm, 2.2 mm, 2.3 mm, 2.4 mm,
2.5 mm,
2.6 mm, 2.7 mm, 2.8 mm, 2.9 mm, or 3.0 mm.
[0074] Aspects of the above process can be used to produce metal strips
as described.
Further, as discussed, the metal strips can be processed using the disclosed
continuous heat
treatment processes to produce a heat treated article. In some aspects, the
entire process to
produce a metal strip and heat treat the metal strip is continuous. The metal
strip can be then
be subjected to the described heat treatment process.
Examples
[0075] These illustrative examples are given to introduce the reader to
the general
subject matter discussed here and are not intended to limit the scope of the
disclosed
concepts. The following sections describe various additional features and
examples with
reference to the drawings in which like numerals indicate like elements, and
directional
descriptions are used to describe the illustrative embodiments but, like the
illustrative
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embodiments, should not be used to limit the present disclosure. The elem ents
included in
the illustrations herein may not be drawn to scale.
[0076] Example 1
[0077] A direct chill cast ingot of an alloy containing 0.62 wt.% Mg,
0.75 wt.% Si,
0.21 wt.% Cu, 0.13 wt.% Mn, 0.2 wt.% Fe and 0.02 wt.% Ti was scalped,
homogenized, hot
and cold rolled to a final 0.9 mm gauge. The cold rolled strip of coil
(Example 1) was
solution heat treated between 540 C and 575 C, rapidly cooled to below 50
C, and
thermally spiked in a furnace set at 220 C in a continuous process where
strip is travelling at
60 meters/min before coiling. There was no intentional (i.e., only natural)
cooling in between
thermal spiking and coiling at the end of the process. The strip was sampled
before coiling at
a flying shear location of the line and after cooling on a finishing line.
[0078] The samples taken before and after the coiling were tested after 6
days of
continuous anneal solution heat treatment ("CASH") using ASTM samples in as-is
and paint
bake conditions (2 + 20 min @185 C - referred to as T8X). Table 5 shows
that the
transverse yield strength of the sheet sample taken at the flying shear and
before coiling
exhibit 117 and 229 MPa in the as-is and paint bake tempers respectively, and
they are only
marginally higher than typical values expected from this alloy. However, the
yield strengths
(YS) values are higher in both tempers in the coil cooled samples, which is
very surprising as
traditional products without thermal spiking and coiled at similar
temperatures do not exhibit
such high properties. Such products are generally produced by subjecting a
coil in the T4
temper to a separate batch ageing heat treatment. Without being bound by
theory, it is
believed that the disclosed thermal spiking process accelerates the age
hardening process
during coil cooling.
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[0079] Table 5: Transverse Tensile Properties of Coil Example 1
Condition Temper Yield Strength UTS EIT (%)
(Mp a) (Mp a)
Before Coil T4 117 237 24.4
Cooling T8X 229 296 18.9
After Coil T4 237 322 20.4
Cooling T8X 308 347 14.9
Note: T8X is 2 % + 20 min at 185 C
[0080] Examples 2-5
[0081] Direct chilled cast ingots of four different alloys, with the
compositions shown
in Table 6, were scalped, homogenized, hot and cold rolled to the final gauge.
The cold rolled
strip of coil as in Example 1 was solution heat treated between 540 C and 575
C, rapidly
cooled to below 50 C and thermally spiked in a furnace set 250 C in a
continuous process
where strip is travelling at 60 meters/min before coiling at the end of the
line. The strip was
sampled before coiling at flying shear location of the line and after cooling
on a finishing
line.
[0082] Table 6: Compositions of Examples 2-5 in wt. %
Alloys Al Si Fe Cu Mn Mg Cr Ti
2 98.3 0.59 0.21 0.12 0.09 0.62 0.01 0.03
3 98.1 0.81 0.24 0.09 0.08 0.62 0.03 0.02
4 98.1 1.05 0.22 0.02 0.14 0.44 0.00 0.03
98.0 0.80 0.25 0.09 0.08 0.65 0.01 0.03
[0083] Samples of Examples 2-5 taken before and after the coiling were
tested after a
few days of cash using ASTM samples in as-is and T8X (2%+20min @185 C)
conditions,
except for coil Example 3 which was tested using JIS sample and paint bake
temper of
(2%+20min @170 C). Table 7 summarizes the tensile properties of the Example 2-
5 samples
taken at the flying shear and the finishing line. Table 7 shows that all four
alloys exhibit
significantly higher strengths in coil cooled sample as opposed to the flying
shear samples
before coil cooling confirming the results of Example 1.
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[0084] Table 7: Transverse Tensile Properties of Examples 2-5 Thermally
Spiked at
250 C
Alloys Ga (mm) Condition Temper YS Mpa UTS Mpa EIT%
2 1 Before coil T4 97 203 26.5
cooling T8X 190 255 18.4
After coil T4 133 233 23.9
cooling T8X 251 303 18.1
3 1.4 Before coil T4 115 227 24.3
cooling T8X 222 282 19.0
After coil T4 212 290 18.4
cooling T8X 11111111" "1111111111111111I
4 0.95 Before coil T4 99 218 27.0
cooling T8X 216 280 20.8
After coil T4 198 286 22.1
cooling T8X 269 313 18.3
0.95 Before coil T4 100 220 26.3
cooling T8X 232 294 17.1
After coil T4
............260.......................3.3Ø......................1.8:.7.......
....
cooling T8X
Note: T8X is 2% plus 20 min at 185 C
[0085] Examples 6-8
[0086] Like Examples 2-5, three cold rolled coils of Alloy Ex. 4 were
solutionized in
a continuous heat treatment line and thermally spiked ranging from 200 and 250
C and, with
no intentional cooling (i.e., only natural air cooling) after thermal spiking,
coiling at the end
of the line. The samples of Examples 6-8 obtained from before coiling at the
flying shear and
coiled from the finishing line were tested using the ASTM samples in both as-
is and T8X
tempers. The results of this trial as summarized in Table 8 show that the
thermally spiked
and coil cooled samples exhibit higher strengths compared to the flying shear
samples,
confirming the effects of thermal spiking and the results of previous
examples.
[0087] The same coils for Examples 6-8, listed in Table 8, were re-
solutionized the
same way as the first time but with reheater set in auto mode, 100 C and 150
0C,
respectively. The results from the resolution coils are summarized in Table 9,
which shows
that an increase in thermal spiking temperature results in higher strengths
but the extent of the
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increase is lower than those seen at >200 C. As shown in these results, the
thermal spiking
temperature has significant impact on the strength of the coil cooled samples.
This
observation shows that with proper choice of alloy and thermal temperatures,
it is possible to
produce different combination of tensile properties without the requirement of
an additional
batch ageing process.
[0088] Table 8: Transverse Tensile Properties Thermally Spiked Alloy Ex.
4 Coils
Examples 6-8
Alloys Coil Cooling Temper YS (Mpa) UTS (Mpa) EIT %
6 200 Before T4 104 214 24.3
After T8X 208 271 14.6
Before T4 150 242 19.3
After T8X 257 311 19.3
7 250 Before T4 92 207 27.0
After T8X 201 267 19.3
Before T4 190 279 22.6
After T8X 257 303 19.0
8 250 Before T4 97 211 25.5
After T8X 218 283 19.7
Before T4 k k
After T8X 268 314 19.1
Notes: T8X is 2% plus 20 min @ 185 C
[0089] Table 9: Transverse Tensile Properties of Coils of Examples 6-8
and
Resolutionized and Thermally Spiked at Lower Temperatures
Alloys Spike Coil Cooling Temper Yield St. UTS (Mpa) EIT %
Temp (C) (Mpa)
6 Normal Before T4 112 236 29.3
After T4 111 232 28.6
T8X 202 270 19.6
7 100 Before T4 108 229 28.4
After T4 101 221 27.9
T8X 226 287 19.8
8 150 Before T4 111 238 26.3
After T4 110 228 26.4
T8X 238 299 20.3
Notes: T8X is 2% plus 20 min @185 C
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[0090] Examples 9-10
[0091] The objective of this trial was to twofold: first, examine the
effects of heating
rate during thermal spiking via change in the line speeds (52 m/min vs 41
m/min) on the
strength of AA6111 coils and, second, compare tensile properties of AA6111
with typical
5xxx alloys supplied in H3X tempers.
[0092] A pair of 2mm gauge cold rolled coils (Examples 9 and 10) of
AA6111 alloy
containing 0.76 wt.% Cu, 0.74 wt.% Mg, 0.66 wt.% Si, 0.27 wt.% Fe and 0.74
wt.% Mn were
solutionized between 520 to 560 C, rapidly cooled below 50 C, thermally
spiked in a
furnace at 250 C before coiling at the end of the continuous process. Coils
of Examples 9
and 10 were heat treated at 52 meter/min and 41 meter/min, respectively. The
samples
obtained from each coil on a finishing line and tested using the ASTM samples
in both as-is
and T8X tempers. The results of this trial are summarized in Table 10. Both
coils processed
at two line speeds show very similar properties in both T4 and T8X tempers,
suggesting no
major effect on the tensile properties from change in line speeds ranging from
41 m/min to 52
m/min strip speed. The higher strengths in T4 temper potentially could be used
for structural
parts offering downgauging possibility or eliminate postformed heat
treatments.
[0093] Table 10: Transverse Tensile Properties of 2 mm gauge AA6111 Coils
Examples 9 and 10 Solutionized and Thermally Spiked before coiling
Line Yield UTS
Alloys Speed Temper Strength (mp EIT (%)
(m/min) (Mpa)
9 52 T4 260 360 22
T8X 322 371 17
41 T4 266 361 19
T8X 333 375 18
[0094] Table 11: Typical properties of Commonly Used 5xxx Alloys in
Different
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[0095] Tempers
AA Alloys Temper Yield Strength UTS (Mpa)
Total Elongation
(Mpa) (A)
5052 H32 195 230 12
5052 H34 215 260 10
5052 H36 240 310 8
5052 H38 290 255 7
5083 H32 230 315 16
5086 H32 205 290 12
5086 H34 255 325 10
5454 H32 205 275 10
5454 H34 240 305 10
[0096] Table 11 summarizes typical ASTM tensile properties of commonly
used 5xxx
alloys. The YS, UTS and total elongations values range from 190 to 290 MPa and
230 and
325 MPa and 7 to 16%, respectively. The YS of AA6111 coils in Table 10 is
close to 5086-
H34 with significantly higher total elongation. This suggest that AA6111
material produced
by the process described herein could replace 5086-H34 product while offering
better total
elongation. The same alloy could be produced with lower strengths by thermal
spiking at
lower temperatures to match strengths of other AA5xxx products. Different
combinations of
strength could also be achieved by changing alloy chemistries along with other
process
variables.
[0097] The thermally spiked AA6xxx does not exhibit any major natural
ageing. The
characteristics together with comparable strengths and total elongations
offers a very
attractive alternative to 5xxx products where high formability are required.
[0098] Example 11
[0099] A direct chilled cast ingot of AA6111 alloy containing 0.69 wt.%
Mg, 0.57%
wt.% Si, 0.51 wt.% Cu, 0.19 wt.% Mn, 0.23 wt.% Fe and 0.01 wt.% Ti was
scalped,
homogenized, hot and cold rolled to a final 2.3 mm gauge. The cold rolled
strip of coil was
solution heat treated between 525 C, rapidly cooled to below 50 C, and
thermally spiked in
a furnace to heat up strip to about 190 C in a continuous process and rewound
in a coil wide
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sidewall temperature of about 135 C. The line speed was modulated between 17
to 20
meters/min to ensure strip temperature at the exit of the furnace close to 190
C. There was
no intentional cooling in between thermal spiking and coiling at the end of
the process. The
coil temperature decreased from 135 C to 85 C at about 2.8 C/h and further
cooling to
ambient would be less than 2 C/hour. The coil was sampled after 5 days of the
heat
treatment and tested using ASTM samples in as-is and different paint bake
tempers.
[00100] Table 12 shows the average transverse ASTM tensile properties of
the sheet
sample taken from the coil cooled samples. The yield strength (YS) and
ultimate tensile
strength (UTS) of the coil cooled sample are 277 and 344 Mpa respectively with
a 17% total
elongation value. These properties are significantly different from AA6111
coils normally
produced with coiling temperatures below 100 C, typically exhibiting 125 Mpa
YS, 230
1ViPa UTS, and 24% total elongation. The properties of the coil are
characteristic of aged
tempers obtained close to 50 h of ageing at 140 C. Without being bound by
theory, the
thermal spiking is accelerating the hardening process during coil cooling. The
alloy shows
marginal increase in strength if aged at elevated temperatures with and
without prestrain s as
shown in Table 12. The thermal spiking process produces coils with strength at
relatively
short ageing times and better elongations than expected from a typical batch
annealing
process with less than 14% elongation.
[00101] Table 12: Transverse Tensile Properties of Example 11 (AA6111)
Temper Yield Strength (Mpa) UTS (Mpa) Total Elongation (%)
T4 277 344 17
20 min @ 180 C 286 330 13
2% + 20 min @ 180 C 301 336 17
30 min 225 C 285 329 14
[0100] The foregoing description of the embodiments, including
illustrated
embodiments, has been presented only for the purpose of illustration and
description and is
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not intended to be exhaustive or limiting to the precise forms disclosed.
Numerous
modifications, adaptations, and uses thereof will be apparent to those skilled
in the art.
[0101] As
used below, any reference to a series of embodiments is to be understood
as a reference to each of those embodiments disjunctively (e.g., "Embodiments
1-4" is to be
understood as "Embodiments 1, 2, 3, or 4").
[0102]
Embodiment 1 is a process for producing a heat treated aluminum alloy
comprising casting a metal strip; solutionizing the cast metal strip at a line
speed to produce a
solutionized metal strip; air cooling the solutionized metal strip to produce
a cooled metal
strip; thermally spiking the cooled metal strip at a temperature from 150 C
to 300 C
continuously at the line speed to produce a thermally spiked metal strip; and
coiling the
thermally spiked metal strip to produce a coiled metal strip.
[0103]
Embodiment 2 is the process of Embodiment 1, further comprising cooling the
thermally spiked metal strip after thermally spiking.
[0104]
Embodiment 3 is the process of any of the embodiments, wherein cooling the
thermally spiked metal strip comprises air cooling the thermally spiked metal
strip.
[0105]
Embodiment 4 is the process of Embodiment 1, wherein only natural cooling
occurs of the thermally spiked metal strip occurs between thermal spiking and
coiling.
[0106]
Embodiment 5 is the process of any of the embodiments, wherein coiling the
thermally spiked metal strip is carried out continuously at the end of a
continuous line.
[0107]
Embodiment 6 is the process of any of the embodiments, wherein the cooling
of the thermally spiked metal strip is at a rate of less than 10 C/hour.
[0108]
Embodiment 7 is the process of any of the embodiments, wherein the cooling
of the thermally spiked metal strip is at a rate of less than 2 C/hour.
[0109]
Embodiment 8 is the process of any of the embodiments, wherein the coiling
of the thermally spiked metal strip is at a temperature of 70 C to 130 C.
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[0110] Embodiment 9 is the process of any of the embodiments, wherein the
coiling
of the thermally spiked metal strip is performed at a temperature above 60 C.
[0111] Embodiment 10 is the process of any of the embodiments, wherein
the line
speed is at least 10 meters/min.
[0112] Embodiment 11 is the process of any of the embodiments, wherein
the line
speed is from 10 meters/min to 120 meters/min.
[0113] Embodiment 12 is the process of any of the embodiments, wherein
the thermal
spike temperature is from 150 C to 280 C.
[0114] Embodiment 13 is the process of any of the embodiments, wherein
the thermal
spike temperature is from 200 C to 250 C.
[0115] Embodiment 14 is the process of any of the embodiments, wherein
casting a
metal strip comprises continuous casting.
[0116] Embodiment 15 is the process of any of the embodiments, wherein
casting a
metal strip comprises Direct Chill (DC casting).
[0117] Embodiment 16 is the process of any of the embodiments, further
comprising
homogenizing, hot rolling, and cold rolling the metal strip after casting and
before
solutionizing.
[0118] Embodiment 17 is the process of any of the embodiments, wherein
thermally
spiking the cooled metal strip is carried out in a reheater furnace with a
length of at least 12
meters.
[0119] Embodiment 18 is the process of any of the embodiments, wherein
the
solutionizing temperature is from about 480 C to about 590 C.
[0120] Embodiment 19 is the process of any of the embodiments, wherein
air cooling
the solutionized metal strip comprises cooling the solutionized metal strip to
less than 50 C.
41
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[0121] Embodiment 20 is a heat treated metal strip formed from the
process of any of
the embodiments.
42
