U.S. patent application number 14/816280 was filed with the patent office on 2016-02-11 for aluminum alloy for heat exchanger fins.
This patent application is currently assigned to NOVELIS INC.. The applicant listed for this patent is NOVELIS INC.. Invention is credited to Hany Ahmed, Kevin Michael Gatenby, Andrew D. Howells, Jyothi Kadali.
Application Number | 20160040947 14/816280 |
Document ID | / |
Family ID | 53785797 |
Filed Date | 2016-02-11 |
United States Patent
Application |
20160040947 |
Kind Code |
A1 |
Gatenby; Kevin Michael ; et
al. |
February 11, 2016 |
ALUMINUM ALLOY FOR HEAT EXCHANGER FINS
Abstract
An aluminum alloy fin stock material comprising about 0.9-1.2
wt. % Si, 0.3-0.5 wt. % Fe, 0.20-0.40 wt. % Cu, 1.0-1.5 wt. % Mn,
0-0.1% Mg and 0.0-3.0% Zn, with remainder Al and impurities at
.ltoreq.0.15 wt. %. The aluminum alloy fin stock material is
produced in a form of a sheet by a process comprising the steps of
direct chill casting an ingot, hot rolling the ingot after the
direct chill casting, cold rolling the aluminum alloy to an
intermediate thickness, inter-annealing the aluminum alloy cold
rolled to an intermediate thickness at a temperature between 200
and 400.degree. C., and cold rolling the material after
inter-annealing to achieve % cold work (% CW) of 20 to 40%. The
aluminum alloy fin stock material possesses an improved combination
of one or more of pre- and/or post-brazes strength, conductivity,
sag resistance and corrosion potential. It is useful for
fabrication of heat exchanger fins.
Inventors: |
Gatenby; Kevin Michael;
(Johns Creek, GA) ; Ahmed; Hany; (Atlanta, GA)
; Howells; Andrew D.; (Kingston, CA) ; Kadali;
Jyothi; (Atlanta, GA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NOVELIS INC. |
Atlanta |
GA |
US |
|
|
Assignee: |
NOVELIS INC.
Atlanta
GA
|
Family ID: |
53785797 |
Appl. No.: |
14/816280 |
Filed: |
August 3, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62033879 |
Aug 6, 2014 |
|
|
|
Current U.S.
Class: |
165/185 ;
148/439; 148/552; 228/183; 420/532 |
Current CPC
Class: |
B23K 1/0012 20130101;
C22F 1/04 20130101; F28F 21/084 20130101; C22C 21/02 20130101; C22F
1/043 20130101; C22F 1/053 20130101; C22C 21/00 20130101; B22D
21/04 20130101; C22C 21/10 20130101 |
International
Class: |
F28F 21/08 20060101
F28F021/08; C22F 1/043 20060101 C22F001/043; C22F 1/04 20060101
C22F001/04; B23K 1/00 20060101 B23K001/00; C22C 21/02 20060101
C22C021/02; C22C 21/10 20060101 C22C021/10; C22C 21/00 20060101
C22C021/00; B22D 21/04 20060101 B22D021/04; C22F 1/053 20060101
C22F001/053 |
Claims
1. An aluminum alloy, comprising about 0.9-1.2 wt. % Si, 0.3-0.5
wt. % Fe, 0.20-0.40 wt. % Cu, 1.0-1.5 wt. % Mn, 0-0.1% wt. Mg and
0.0-3.0% wt. Zn, with remainder Al and impurities at .ltoreq.0.15
wt. %.
2. The aluminum alloy of claim 1, comprising about 0.9-1.2 wt. %
Si, 0.3-0.5 wt. % Fe, 0.20-0.40 wt. % Cu, 1.0-1.5 wt. % Mn, 0-0.1
wt. % Mg and 0.2-3.0% wt. Zn, with remainder Al and impurities at
.ltoreq.0.15 wt. %.
3. The aluminum alloy of claim 1, comprising about 0.9-1.2 wt. %
Si, 0.3-0.5 wt. % Fe, 0.20-0.40 wt. % Cu, 1.2-1.4 wt. % Mn, 0-0.1
wt. % Mg and 0.0-3.0 wt. % Zn, with remainder Al and impurities at
.ltoreq.0.15 wt. %.
4. The aluminum alloy of claim 1, wherein one or more of Zr, V, Cr
or Ni is present at below 0.05 wt. %.
5. The aluminum alloy of claim 1, wherein the alloy is in a form of
an aluminum alloy sheet.
6. The aluminum alloy of claim 1, wherein the alloy is in a form of
an aluminum alloy sheet produced by a process comprising: direct
chill casting the aluminum alloy into an ingot; hot rolling the
ingot after the direct chill casting into a hot rolled sheet; after
the hot rolling, cold rolling the hot rolled sheet into an
intermediate thickness sheet; after cold rolling, inter-annealing
the the intermediate thickness sheet at 200-400.degree. C.; and,
after inter-annealing, cold rolling the intermediate thickness
sheet to achieve % cold work (% CW) of 20 to 40%, resulting in the
aluminum alloy sheet having a thickness of 70-100 .mu.m.
7. The aluminum alloy of claim 5, wherein the aluminum alloy sheet
has ultimate tensile strength of one or both of: at least 200 MPa,
measured in pre-brazed condition, or at least 150 MPa, measured
post-brazing.
8. The aluminum alloy of claim 5, wherein the aluminum alloy sheet
has corrosion potential of -740 mV or less, measured
post-brazing.
9. The aluminum alloy of claim 5, wherein the aluminum alloy sheet
has electrical conductivity of 43-47 IACS, measured
post-brazing.
10. The aluminum alloy of claim 6, wherein the aluminum alloy sheet
has ultimate tensile strength of one or both of: at least 200 MPa,
measured in pre-brazed condition, or at least 150 MPa, measured
post-brazing.
11. The aluminum alloy of claim 6, wherein the aluminum alloy sheet
has corrosion potential of -740 mV or less, measured
post-brazing.
12. The aluminum alloy of claim 6, wherein the aluminum alloy sheet
has electrical conductivity of 43-47 IACS, measured
post-brazing.
13. A heat exchanger comprising the aluminum alloy of claim 1.
14. The heat exchanger of claim 12, wherein the heat exchanger is a
motor vehicle heat exchanger.
15. The heat exchanger of claim 12, wherein the heat exchanger is a
radiator, a condenser or an evaporator.
16. A process of making a fin stock aluminum alloy sheet,
comprising: direct chill casting into an ingot an aluminum alloy
comprising 0.9-1.2 wt. % Si, 0.3-0.5 wt. % Fe, 0.20-0.40 wt. % Cu,
1.0-1.5 wt. % Mn, 0-0.1 wt. % Mg and 0.0-3.0 wt. % Zn, with
remainder Al and impurities at .ltoreq.0.15 wt. %; hot rolling the
ingot after the direct chill casting into a hot rolled sheet; after
the hot rolling, cold rolling the aluminum alloy into an
intermediate thickness sheet; after cold rolling, inter-annealing
the intermediate thickness sheet at 200-400.degree. C.; and, after
inter-annealing, cold rolling the intermediate thickness sheet to
achieve % cold work (% CW) of 20 to 40%, resulting in the finstock
aluminum alloy sheet having a thickness of 70-100 .mu.m.
17. The process of claim 16, wherein the fin stock aluminum alloy
sheet has ultimate tensile strength of one or both of: at least 200
MPa, measured in pre-brazed condition, or at least 150 MPa,
measured post-brazing.
18. The process of claim 16, wherein the fin stock aluminum alloy
sheet has a corrosion potential of -740 mV or less, measured
post-brazing.
19. The process of claim 16, wherein the fin stock aluminum alloy
sheet has electrical conductivity of 43-47 IACS, measured
post-brazing.
20. A process of making a heat exchanger comprising joining by
brazing at least one first aluminum alloy form fabricated from the
aluminum alloy of claim 1 with a second aluminum alloy form,
comprising: assembling and securing the two or more aluminum forms
together; and, heating the two or more aluminum forms to a brazing
temperature until joints are created among the two or more aluminum
forms by capillary action.
21. A heat exchanger fin fabricated from the aluminum alloy of
claim 1.
Description
PRIOR RELATED APPLICATIONS
[0001] The present application claims the benefit of U.S.
Provisional Application Ser. No. 62/033,879 filed Aug. 6, 2014, the
contents of which is incorporated herein by reference in its
entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to the fields of material
science, material chemistry, metallurgy, aluminum alloys, aluminum
fabrication, and related fields. The present invention provides
novel aluminum alloys for use in the production of heat exchanger
fins, which are, in turn, employed in various heat exchanger
devices, for example, motor vehicle radiators, condensers,
evaporators and related devices.
BACKGROUND
[0003] The automotive heat exchanger industry presents a number of
demands on the aluminum materials used for production of heat
exchanger fins ("fin stock materials"). These demands may be
difficult to balance. When heat exchanger devices are produced,
their parts are typically joined by brazing, which requires
aluminum fin stock materials to have good brazing performance,
strong pre-braze mechanical properties and high post-braze. In
order to make heat exchangers lighter, for example, to improve
automobile fuel efficiency, it is desirable for aluminum fin stock
material to be thinner. At the same time, heat exchanger fins also
must conduct significant quantities of heat. Thinner fin stock
aluminum alloys may have reduced strength and performance during
brazing. Furthermore, aluminum fin stock material requires an
appropriate corrosion potential for good corrosion performance of
the heat exchanger. For example, it may be desirable for the heat
exchanger fins to have lower corrosion potential than the remainder
of the heat exchanger, so that the fins act sacrificially.
Desirable aluminum fin stock material would possess the properties
and parameters that balance the above requirements. Accordingly, it
is desirable to produce aluminum fin stock material that would have
a required combination of thickness (gauge), would be able to
withstand brazing and would exhibit appropriate mechanical
characteristics before, during and after brazing, strength and
conductivity characteristics suitable for high performance heat
exchanger applications and suitable corrosion potential. In
addition, it is desirable to produce aluminum fin stock material
from an input metal that incorporates scrap aluminum in order to
produce fin stock material in an environmentally friendly and
cost-effective manner.
SUMMARY
[0004] The terms "invention," "the invention," "this invention" and
"the present invention," as used in this document, 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.
Covered embodiments of the invention are defined by the claims, not
this summary. This summary is a high-level overview of various
aspects of the invention 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 understood by reference to appropriate
portions of the entire specification, any or all drawings and each
claim.
[0005] The present invention provides improved aluminum alloy fin
stock material that possesses a combination of characteristics and
properties that make it suitable for production of heat exchanger
fins, to be used, for example, in heat exchangers, such as those
employed in the automotive industry. In one example, the improved
aluminum alloy fin stock material according to the embodiments of
the present invention can be produced in a sheet form at desired
thickness (gauge) that is suitable for production of light-weight
heat exchange fins for automotive radiators. The aluminum alloy fin
stock material according to the embodiments of the present
invention can be brazed and exhibits strength characteristics
before, during and after brazing that make it attractive for
automotive heat exchanger applications. More specifically, improved
aluminum alloy fin stock material according to the embodiments of
the present invention possesses pre-braze strength characteristics
that reduce fin crush problems during brazing. The aluminum alloy
fin stock material according to the embodiments of the present
invention also possesses sufficiently high thermal conductivity
suitable for heat exchanger applications, and has a corrosion
potential that is sufficiently negative for the fins to act in a
sacrificial manner during corrosion of the heat exchanger. In
summary, the improved aluminum alloy fin stock material according
to the embodiments of the present invention possesses a combination
of suitable pre- and post-braze strength, thermal conductivity, and
anodic corrosion potential values suitable for automotive fin
exchanger applications. At the same time, the aluminum alloy fin
stock material according to the embodiments of the present
invention can be produced from input aluminum that is at least in
part recycle-friendly. More specifically, the improved aluminum
alloy fin stock material according to the embodiments of the
present invention contains levels of non-aluminum constituents, for
example, Cu, Fe, Mn and Zn, that are compatible with the levels of
these elements found in certain scrap aluminum as input metal.
[0006] The improved aluminum alloy fin stock material according to
the embodiments of the present invention is produced in sheet form.
To produce the material, the present invention provides processes
for producing improved aluminum alloy fin stock material, which
incorporate one or more of casting, rolling, or annealing steps. It
is to be understood that, in some embodiments, the process steps
employed during production of the improved aluminum alloy fin stock
material confer beneficial properties and characteristics on the
material. Therefore, the processes for producing the aluminum alloy
fin stock material may be employed, in some cases, to describe and
define the material itself. Accordingly, embodiments of the
invention described using process steps are included within the
scope of the present invention. For example, in some embodiments,
the improved aluminum alloy fin stock material of the invention is
produced in cold-worked form, which results in strain hardening and
improved tensile strength characteristics of the resulting
material. In one embodiment, the aluminum alloy fin stock material
of the invention may be produced by a process that involves direct
chill casting and cold work (cold rolling) to produce desirable
pre-braze temper, for example, H14 temper. In some other
embodiments, the improved fin stock aluminum alloy material can be
produced in various other strain-hardened pre-braze tempers, such
as H16, H18 or other H1X tempers. The process for producing the
aluminum alloy fin stock material may also involve hot rolling
after direct chill casting, and inter-annealing prior to final cold
rolling steps (for example, between intermediate and final cold
rolling steps).
[0007] The aluminum alloy fin stock material according to the
embodiments of the present invention can be used in various
applications, for example, for manufacturing fins for heat
exchangers. In one example, the improved aluminum alloy fin stock
material of the present invention is useful for high performance,
light weight automotive heat exchangers. More generally, the
aluminum alloy fin stock material according to the embodiments of
the present invention can be used in motor vehicle heat exchangers
such as radiators, condensers and evaporators. As discussed above,
the compositions and the processes for producing the improved
aluminum alloy fin stock material of the present invention lead to
a material possessing a combination of beneficial characteristics
and properties that make it suitable for manufacturing heat
exchanger fins. For example, the aluminum alloy fin stock material
of the present invention displays beneficial combination of one or
more of the following characteristics: pre- and post-braze
mechanical properties, such as tensile strength and post-braze sag
resistance, heat conductivity and corrosion potential. However, the
uses and applications of the improved aluminum alloy fin stock
material of the present invention are not limited to automotive
heat exchangers and other uses are envisioned. It is to be
understood that the characteristics and properties of the aluminum
alloy fin stock material of the present invention can also be
beneficial for uses and applications other than the production of
automotive heat exchanger fins. For example, the improved aluminum
alloy fin stock material of the present invention can be used for
manufacture of various devices employing heat exchangers and
produced by brazing, such as devices employed in heating,
ventilation, and air conditioning (HVAC).
[0008] The present invention includes aluminum alloys. One
exemplary embodiment of the present invention is an aluminum alloy
comprising about 0.9-1.2 wt. % Si, 0.3-0.5 wt. % Fe, 0.20-0.40 wt.
% Cu, 1.0-1.5 wt. % Mn, 0-0.1 wt. % Mg and 0.0-3.0 wt. % Zn, with
remainder Al and impurities at .ltoreq.0.15 wt. %. One more
exemplary embodiment of the present invention is an aluminum alloy
comprising about 0.9-1.2 wt. % Si, 0.3-0.5 wt. % Fe, 0.20-0.40 wt.
% Cu, 1.0-1.5 wt. % Mn, 0-0.1 wt. % Mg and 0.2-3.0 wt. % Zn, with
remainder Al and impurities at .ltoreq.0.15 wt. %. Another
exemplary embodiment is an aluminum alloy comprising about 1.0-1.15
wt. % Si, 0.3-0.5 wt. % Fe, 0.20-0.40 wt. % Cu, 1.0-1.5 wt. % Mn,
0-0.1 wt. % Mg and 0.0-3.0 wt. % Zn, with remainder Al and
impurities at .ltoreq.0.15 wt. %. Some other examples of the
aluminum alloys of the present invention are as follows: an
aluminum alloy comprising about 0.9-1.2 wt. % Si, 0.3-0.38 wt. %
Fe, 0.20-0.40 wt. % Cu, 1.0-1.5 wt. % Mn, 0-0.1 wt. % Mg and
0.0-3.0 wt. % Zn, with remainder Al and impurities at .ltoreq.0.15
wt. %; an aluminum alloy comprising about 0.9-1.2 wt. % Si, 0.3-0.5
wt. % Fe, 0.35-0.4 wt. % Cu, 1.0-1.5 wt. % Mn, 0-0.1 wt. % Mg and
0.0-3.0 wt. % Zn, with remainder Al and impurities at .ltoreq.0.15
wt. %; an aluminum alloy comprising about 0.9-1.2 wt. % Si, 0.3-0.5
wt. % Fe, 0.20-0.40 wt. % Cu, 1.2-1.4 wt. % Mn, 0-0.1% Mg and
0.0-3.0 wt. % Zn, with remainder Al and impurities at .ltoreq.0.15
wt. %; an aluminum alloy comprising about 0.9-1.2 wt. % Si, 0.3-0.5
wt. % Fe, 0.20-0.40 wt. % Cu, 1.0-1.5 wt. % Mn, 0-0.1 wt. % Mg and
1.5-2.5% Zn, with remainder Al and impurities at .ltoreq.0.15 wt.
%; an aluminum alloy comprising about 1.0-1.15 wt. % Si, 0.3-0.38
wt. % Fe, 0.35-0.40 wt. % Cu, 1.2-1.4 wt. % Mn, 0-0.1 wt. % Mg and
1.5-2.5 wt. % Zn, with remainder Al and impurities at .ltoreq.0.15
wt. %, and an aluminum alloy comprising about 1.0-1.1 wt. % Si,
0.37-0.42 wt. % Fe, 0.27-0.33 wt. % Cu, 1.3-1.35 wt. % Mn,
0.04-0.05 wt. % Mg and 1.5-1.6 wt. % Zn, with remainder Al and
impurities at .ltoreq.0.15 wt. %. In the aluminum alloys of the
present invention, one or more of Zr, V, Cr or Ni can be present at
0 wt. %, below 0.05 wt. %, below 0.04 wt. %, below 0.03 wt. %,
below 0.02 wt. %, or below 0.01 wt. %. [.sup.9] In some embodiments
of the present invention, the aluminum alloy has ultimate tensile
strength of one or both of: at least 200 MPa, measured in
pre-brazed condition, or at least 150 MPa, measured post-brazing.
In one example, the aluminum alloy has ultimate tensile strength of
one or both of: 200-220 MPa, measured in pre-brazed condition, or
150-160 MPa, measured post-brazing. In another example, the
aluminum alloy has ultimate tensile strength of one or both of:
about 210 MPa, measured in pre-brazed condition, or about 150 MPa,
measured post-brazing. The aluminum alloy of the present invention
can have corrosion potential of -740 mV or less, measured
post-brazing. For example, the aluminum alloy can have corrosion
potential of about -750 mV, measured post-brazing. The aluminum
alloy can have conductivity of 43-47 IACS (International Annealed
Copper Standard, which assumes pure copper conductivity for 100%),
measured post-brazing.
[0009] The aluminum alloy according to the embodiments of the
present invention can be produced by a process comprising: direct
chill casting the aluminum alloy into an ingot; hot rolling the
ingot after the direct chill casting; after the hot rolling, cold
rolling the aluminum alloy to an intermediate thickness; after cold
rolling, inter-annealing the aluminum alloy rolled to the
intermediate thickness at a temperature between 200 and 400.degree.
C. (200-400.degree. C.); and, after inter-annealing, cold rolling
the aluminum alloy to achieve % cold work (% CW) of 20 to 40%,
resulting in a sheet having a thickness of 70-100 .mu.m, 70-90
.mu.m, 75-85 .mu.m, or 77-83 gm. % CW achieved in the
above-described process can be 30 to 40%. The inter-annealing can
be performed at a temperature between 320 and 370.degree. C.
(320-370.degree. C.), between 290 and 360.degree. C.
(290-360.degree. C.) or between 340 and 360.degree. C.
(340-360.degree. C.). The inter-annealing time can be 30 to 60
minutes. Embodiments of the present invention include the above
processes of making aluminum alloys of the present invention.
[0010] Embodiments of the present invention include objects and
apparatuses, for example, a heat exchanger, comprising the aluminum
alloy of the present invention. The heat exchanger can be a motor
vehicle heat exchanger. The heat exchanger can be a radiator, a
condenser or an evaporator. Embodiments of the present invention
also include processes for making objects and apparatuses
comprising alloys of the present invention. One example of such a
process is a process of making a heat exchanger, comprising joining
by brazing at least one first aluminum alloy form fabricated from
the aluminum alloy of the present invention with a second aluminum
alloy form, comprising: assembling and securing the two or more
aluminum forms together; heating the two or more aluminum forms to
a brazing temperature until joints are created among the two or
more aluminum forms by capillary action. Uses of the aluminum
alloys of the present invention for fabrication of heat exchanger
fins and other objects and apparatuses are also included within the
scope of the present invention. Other objects and advantages of the
invention will be apparent from the following detailed description
of embodiments of the invention.
DETAILED DESCRIPTION
[0011] Among other things, this document describes innovative
aluminum alloy materials. These innovative aluminum materials can
be referred to as "aluminum alloys," in singular or plural. The
innovative aluminum materials described herein can be fabricated as
sheets by processes that involve hot and/or cold rolling steps to
achieve desirable thickness. Therefore, aluminum alloy materials of
the present invention can be referred to as "sheet aluminum
alloys," "aluminum alloy sheets," "sheets," "strips," or by other
related terms, in singular or plural. The innovative aluminum alloy
materials according to the embodiments of the present application
are suitable for production of fins for heat exchanger apparatuses
and therefore can be termed "fin stock," "fin stock aluminum
alloy," "aluminum alloy for fin production," "aluminum alloy for
heat exchanger fins," "aluminum alloy fin stock material,"
"aluminum alloy fin stock," "fin stock alloy" and other related
terms.
[0012] The properties of aluminum alloy fin stock materials vary
based on their composition. The aluminum alloy fin stock material
according to the embodiments of the present invention possesses a
number of advantageous properties. The aluminum alloy fin stock
material of the present invention is produced in the form of sheets
and possesses a combination of thickness (gauge) and strength
before, during and after brazing that make it suitable for
manufacturing of fins for heat exchanger applications. The aluminum
alloy material according to the embodiments of the present
invention also possesses thermal conductivity and corrosion
potential suitable for fin stock production.
[0013] The aluminum alloy fin stock material according to the
embodiments of the present invention can contain higher content of
one or more of Cu, Si and Fe, in comparison to known fin stock
alloys. The composition of the aluminum alloy fin stock material of
the present invention and/or its production process lead to
improved properties of the material, such as reduction of fin crush
during brazing, higher post-braze strength, improved thermal
conductivity, improved sag resistance and increased anodic
corrosion potential. The aluminum alloy fin stock material
according to the embodiments of the present invention possesses one
or more of strength, heat conductivity and corrosion potential that
is improved in comparison with known alloys used for fin stock
production. The relatively high levels of non-aluminum constituents
in the aluminum alloy fin stock material according to the
embodiments of the present invention allow it to be produced from
input metal that incorporates recycle-friendly aluminum, allowing
for different metal inputs.
[0014] In some embodiments of the present invention, the aluminum
alloy fin stock material is produced by a process comprising a heat
treatment (inter-annealing) step before a final cold rolling step.
Inter-annealing is conducted at a temperature between 200 and
400.degree. C. for a period from about 30 min to 2 hours (in some
embodiments, for a time period of about 1 to 2 hours).
Inter-annealing is followed by cold rolling steps leading to
specified reduction of thickness ("% cold work", defined later in
this document). In some embodiments of the present invention, the
above combination of process steps (inter-annealing followed by
cold rolling) results in increase of pre-braze strength and
improved coarse post-braze grain structure, which leads to improved
sag resistance of the improved aluminum fin stock materials
according to the embodiments of the present invention, and also
affects heat conductivity and corrosion potential, thus leading to
a material having a favorable combination of characteristics and
properties.
Compositions
TABLE-US-00001 [0015] TABLE 1a Alloy constituents (wt. %)* Element
Examples of lower range limit Examples of upper range limit Si 0.9,
1.0, 1.1, 1.15, 1.2, 1.0, 1.1, 1.15, 1.2, 1.25, 1.25, 1.3, 1.35,
1.4, 1.45 1.3, 1.35, 1.4, 1.45, 1.5 Fe 0.25, 0.3, 0.35, 0.37, 0.38,
0.3, 0.35, 0.37, 0.38, 0.4, 0.4, 0.42, 0.45 0.42, 0.45, 0.5 Cu 0.2,
0.25, 0.27, 0.3, 0.33, 0.25, 0.27, 0.3, 0.33, 0.35, 0.35, 0.4 0.4,
0.45 Mn 1.0, 1.1, 1.2, 1.3, 1.35, 1.1, 1.2, 1.3, 1.35, 1.4, 1.4 1.5
Zn 0.0, 0.2, >0.2, 0.21, 0.22, 1.0, 1.5, 1.6, 1.7, 2.0, 0.25
1.0, 1.5, 1.6, 1.7, 2.5, 3.0, 3.5 2.0, 2.5, 3.0 Mg 0, 0.01, 0.02,
0.03, 0.04, 0.01, 0.02, 0.03, 0.04, 0.05, 0.05, 0.06, 0.07, 0.08,
0.09, 0.06, 0.07, 0.08, 0.09, 0.1 0.1
TABLE-US-00002 TABLE 1b Alloy composition examples* Si (wt. %) Fe
(wt. %) Cu (wt. %) Mn (wt %) Zn (wt. %) Mg (wt. %) Range 1 0.9-1.2
0.3-0.5 0.20-0.40 1.0-1.5 0.0-3.0 0.0-0.1 Range 2 0.9-1.2 0.3-0.5
0.20-0.40 1.0-1.5 0.2-3.0 0.0-0.1 Range 3 0.9-1.2 0.3-0.5 0.25-0.35
1.2-1.4 1.5-1.7 0.0-0.05 Range 4 1.0-1.15 0.25-0.38 0.25-0.35
1.1-1.4 0.0-3.0 0.0-0.1 Range 5 1.0-1.15 0.25-0.38 0.25-0.35
1.1-1.4 1.0-3.0 0.0-0.1 Range 6 1.0-1.15 0.30-0.38 0.25-0.35
1.2-1.4 1.5-2.5 0.0-0.1 Range 7 1.0-1.15 0.30-0.38 0.35-0.40
1.2-1.4 1.5-2.5 0.0-0.1 Range 8 0.9-1.2 0.3-0.5 0.35-0.40 1.0-1.5
0.0-3.0 0.0-0.1 Range 9 1.0-1.1 0.37-0.42 0.27-0.33 1.3-1.35
1.5-1.6 0.04-0.05 *Remainder of the alloy is aluminum and the total
of impurities at .ltoreq.0.15 wt. %
[0016] The composition of the aluminum alloys according to the
embodiments of the present invention is illustrated in Tables la
and lb. The content of Si, Cu, Fe, Mn and Zn can fall within the
ranges delimited by a lower range limit and an upper range limit
selected from the limits shown in Table la. A lower range limit can
be delineated by expressions "equal to or more than" (>sign) or
"more than" (>sign), or other related signs and expression, such
as "from . . . ," "higher than" etc. An upper range limit can be
delineated by expressions "equal to or less than" (.ltoreq.sign),
"less than" (<sign) or other related signs and expressions, such
as "to," "less than," etc. Other types of expressions can also be
used to delineate the ranges, such as "between," "in the range of,"
etc. When a range is delineated by only the upper range limit, it
is to be understood that, in some examples falling within such a
range, an element in question may not be present, may not be
present in detectable quantities, or may be present in such low
quantities that they are conventionally not recognized as
meaningful in the field of aluminum alloys. [17] It is to be
understood that, in various embodiments of the alloys described
herein, the predominant element is aluminum (Al), sometimes called
"remainder Al." In other words, the term "remainder" can be used to
describe predominant aluminum (Al) content in the aluminum alloys
described herein. It is also to be understood that the alloys
described herein can comprise various unavoidable impurities not
otherwise specified. In some non-limiting examples, a content of
each impurity can constitute up to 0.05 wt. %. In some other
non-limiting examples, a total content of impurities can constitute
up to 0.15 wt. %. For example, a content of each impurity can be 0
wt. %, below 0.05 wt. %, below 0.04 wt. %, below 0.03 wt. %, below
0.02 wt. %, or below 0.01 wt. %, while a total content of all
impurities can constitute up to 0.15 wt. %. Some non-limiting
examples of impurities are Zr, V, Cr, or Ni. The levels of various
constituents of the alloys can be chosen to fall within the ranges
described throughout this document using various considerations,
some of which are discussed below.
[0017] Si: Among other things, Si content affects melting
temperature of an aluminum alloy. Increasing the content of Si
reduces the melting point of the aluminum alloy. Accordingly, in
order for the aluminum alloy fin stock to be brazeable, Si content
of the alloy should be sufficiently low so that the alloy does not
melt during the brazing cycle. On the other hand, relatively high
Si content in the alloy leads to formation of AlMnSi dispersoids
resulting in beneficial dispersoid strengthening of the matrix and
improved strength characteristics of the alloy. The Si content used
in the fin stock alloy according to the embodiments of the present
invention balances the above factors. Aluminum alloys according to
embodiments of the present invention can comprise, for example,
0.9-1.0, 0.9-1.1, 0.9-1.15, 0.9-1.2, 0.9-1.25, 0.9-1.3, 0.9-1.35,
0.9-1.4, 0.9-1.45, 0.9-1.5, 1.0-1.1, 1.0-1.15, 1.0-1.2, 1.0-1.25,
1.0-1.3, 1.0-1.35, 1.0-1.4, 1.0-1.45, 1.0-1.5, 1.1-1.15, 1.1-1.2,
1.1-1.25, 1.1-1.3, 1.1-1.35, 1.1-1.4, 1.1-1.45, 1.1-1.5, 1.15-1.2,
1.15-1.25, 1.15-1.3, 1.15-1.35, 1.15-1.4, 1.15-1.45, 1.15-1.5,
1.2-1.25, 1.2-1.3, 1.2-1.35, 1.2-1.4, 1.2-1.45, 1.2-1.5, 1.25-1.3,
1.25-1.35, 1.25-1.4, 1.25-1.45, 1.25-1.5, 1.3-1.35, 1.3-1.4,
1.3-1.45, 1.3-1.5, 1.35-1.4, 1.35-1.45, 1.35-1.5, 1.4-1.45, 1.4-1.5
or 1.45-1.5 wt. % Si.
[0018] Cu: Cu in solid solution increases strength of an aluminum
alloy. Increasing Cu content may also lead to formation of Cu
containing A1MnCu dispersoids, which stores Mn and dissolves during
brazing, thus leading to release of Mn into solid solution. This
process results in improved post-braze strength. Relatively high Cu
content of the fin stock alloys according to the embodiments of the
present invention allows for cost reduction and increase in
recycling capacity. Aluminum alloys according to the embodiments of
the present invention can comprise, for example, 0.2-0.25,
0.2-0.27, 0.2-0.3, 0.2-0.35, 0.2-0.4, 0.2-0.45, 0.25-0.27,
0.25-0.3, 0.25-0.33, 0.25-0.35, 0.25-0.4, 0.25-0.45, 0.27-0.3,
0.27-0.33, 0.27-0.35, 0.27-0.4, 0.27-0.45, 0.3-0.33, 0.3-0.35,
0.3-0.4, 0.3-0.45, 0.33-0.35, 0.33-0.4, 0.33-0.45, 0.35-0.4,
0.35-0.45 or 0.4-0.45 wt. % Cu.
[0019] Zn: Zn is typically added to aluminum alloys to move the
corrosion potential towards the anodic end of the scale. In the fin
stock aluminum alloy according to the embodiments of the present
invention, relatively high Zn content of up to 3 wt. % compensates
for the shift in corrosion potential due to increased Si and Cu
content, thus resulting in more anodic corrosion potential,
allowing the fins manufactured from the alloy to act sacrificially
and protect heat exchanger tubes, thus improving in overall
corrosion resistance of the heat exchanger. Aluminum alloys
according to the embodiments of the present invention can comprise,
for example, 0.0-1.0, 0.0-1.5, 0.0-1.6, 0.0-1.7, 0.0-2.0, 0.0-2.5,
0.0-3.0, 0.0-3.5, 0.2-1.0, 0.2-1.5, 0.2-1.6, 0.2-1.7, 0.2-2.0,
0.2-2.5, 0.2-3.0, 0.2-3.5, 0.21-1.0, 0.21-1.5, 0.21-1.6, 0.21-1.7,
0.21-2.0, 0.21-2.5, 0.21-3.0, 0.21-3.5, 1.0-1.5, 1.0-1.6, 1.0-1.7,
1.0-2.0, 1.0-2.5, 1.0-3.0, 1.0-3.5, 1.5-1.6, 1.5-1.7, 1.5-2.0,
1.5-2.5, 1.5-3.0, 1.5-3.5, 1.6-1.7, 1.6-2.0, 1.6-2.5, 1.6-3.0,
1.6-3.5, 1.7-2.0, 1.7-2.5, 1.7-3.0, 1.7-3.5, 2.0-2.5, 2.0-3.0,
2.0-3.5, 2.5-3.0, 2.5-3.5 or 3.0-3.5 wt. % Zn.
[0020] Mn: Mn in solid solution increases strength of an aluminum
alloy but also moves corrosion potential towards a more cathodic
state. (FeMn)-A1.sub.6 or Al.sub.15Mn.sub.3Si.sub.2 dispersoid
increases strength of an aluminum alloy by particle strengthening,
when present in a fine and dense dispersion. Depending on the
composition and solidification rate, Fe, Mn, Al and Si combine
during solidification to form various intermetallic constituents,
i.e. particles within the microstructure, like A1.sub.15(Fe
Mn).sub.3Si.sub.2 or Al.sub.5FeSi or Al.sub.8FeMg.sub.3Si.sub.6, to
name a few. Higher Mn content, particularly in combination with
higher Fe content, may lead to formation of coarse Mn--Fe
intermetallic constituents. Aluminum alloys according to the
embodiments of the present invention can comprise, for example,
1.0-1.1, 1.0-1.2, 1.0-1.3, 1.0-1.35, 1.0-1.4, 1.0-1.5, 1.0-1.1,
1.1-1.2, 1.1-1.3, 1.1-1.35, 1.1-1.4, 1.1-1.5, 1.2-1.3, 1.2-1.35,
1.2-1.4, 1.2-1.5, 1.3-1.35, 1.3-1.4, 1.3-1.5, 1.35-1.4, 1.35-1.5 or
1.4-1.5 wt. % Mn.
[0021] Fe: In an aluminum alloy, Fe can be a part of intermetallic
constituents which may contain Mn, Si, and other elements. It is
often beneficial to control Fe content in an aluminum alloy to
influence the content of coarse intermetallic constituents.
Aluminum alloys according to the embodiments of the present
invention can comprise, for example, 0.25-0.3, 0.25-0.35,
0.25-0.37, 0.25-0.38, 0.25-0.4, 0.25-0.42, 0.25-0.45, 0.25-0.5,
0.3-0.35, 0.3-0.37, 0.3-0.38, 0.3-0.4, 0.3-0.42, 0.3-0.45, 0.3-0.5,
0.35-0.37, 0.35-0.38, 0.35-0.4, 0.35-0.42, 0.35-0.45, 0.35-0.5,
0.37-0.38, 0.37-0.4, 0.37-0.42, 0.37-0.45, 0.37-0.50, 0.38-0.4,
0.38-0.42, 0.38-0.45, 0.38-0.5, 0.4-0.42, 0.4-0.45, 0.4-0.5 or
0.45-0.5 wt. % Fe. [23] Mg contributes to strength of aluminum
through solid solution strengthening. Aluminum alloys according to
the embodiments of the present invention can comprise, for example,
0-0.01, 0-0.02, 0-0.03, 0-0.04, 0-0.05, 0-0.06, 0-0.07, 0-0.08,
0-0.09, 0-0.1, 0.01-0.02, 0.01-0.03, 0.01-0.04, 0.01-0.05,
0.01-0.06, 0.01-0.07, 0.01-0.08, 0.01-0.09, 0.01-0.1, 0.02-0.03,
0.02-0.04, 0.02-0.05, 0.02-0.06, 0.02-0.07, 0.02-0.08, 0.02-0.09,
0.02-0.1, 0.03-0.04, 0.03-0.05, 0.03-0.06, 0.03-0.07, 0.03-0.08,
0.03-0.09, 0.03-0.1, 0.04-0.05, 0.04-0.06, 0.04-0.07, 0.04-0.08,
0.04-0.09, 0.04-0.1, 0.05-0.06, 0.05-0.07, 0.05-0.08, 0.05-0.09,
0.05-0.1, 0.06-0.07, 0.06-0.08, 0.06-0.09, 0.06-0.1, 0.07-0.08,
0.07-0.09, 0.07-0.1, 0.08-0.09, 0.08-0.1, 0.09-0.1 wt % Mg.
[0022] In the aluminum alloys according to the embodiments of the
present invention, there is no intentionally added Zr, V, Cr, or
Ni, expect for the impurities found in scrap input aluminum. In the
aluminum alloy according to the embodiments of the present
invention, such impurities may be 0%, below 0.05%, below 0.04%,
below 0.03%, below 0.02%, or below 0.01% provided the sum of all
impurities is not more than 0.15%. Some exemplary embodiments of
the fin stock aluminum alloy compositions are described in the
"Summary" section of this document.
Processes for Making Aluminum Alloy Fin Stock Material
[0023] The processes for making or fabricating aluminum alloy fin
stock material described herein, as well as for fabricating the
objects using aluminum alloy fin stock material of the present
invention, are also included within the scope of the present
invention. Aluminum alloy fin stock material described herein can
be fabricated by the processes that include at least some of the
technological steps described in this document. It is to be
understood that, unless specifically set forth as such,
descriptions of the processes contained in this document are
non-limiting with respect to the claimed embodiments of the present
invention. The process steps described herein can be combined and
modified in various ways and suitably employed for fabricating
aluminum alloys or forms and objects from such alloys. Process
steps and conditions that are not explicitly described herein, yet
commonly employed in the areas of metallurgy and aluminum
processing and fabrication, can also be incorporated into the
processes falling within the scope of the present invention.
Aluminum alloy fin stock materials according to the embodiments of
the present invention can employ the process steps and the
conditions discussed below.
[0024] A process for producing aluminum alloy fin stock materials
can employ direct chill (DC) casting an aluminum alloy into an
ingot. Following DC casting, the process comprises hot rolling of
the ingot. The ingots produced by DC casting are preheated for hot
rolling. The preheating temperature and duration of hot rolling are
finely controlled to preserve a large grain size and high strength
after the finished fin stock is brazed. In the processes according
to the embodiments of the present invention, for hot rolling, the
ingots can be preheated to up to 500.degree. C., for example, to
450-480.degree. C., in a furnace for up to 12 hours at a suitable
heating rate, for example 50.degree. C./hr, followed by maintaining
the temperature ("soak" or "soaking") at 450-500.degree. C., for
example, at 470-480.degree. C., for 5-7 hours. Following preheating
and soaking, the ingots are hot rolled to 2-10 mm (for example, 3-5
mm or 3.5-4 mm) thickness, which may be referred to as "exit gauge"
after hot rolling.
[0025] A process for producing aluminum alloy fin stock materials
comprises cold rolling steps to produce desired thickness (gauge)
and other properties of the material. For example, following a hot
rolling step, the hot rolled aluminum alloy is cold-rolled to 1-2
mm, for example, to 1 mm, thickness or gauge (initial cold rolling
gauge) during an initial cold rolling step, which can comprise
multiple cold rolling passes, followed by further cold rolling to
100-200 .mu.m thickness or gauge (intermediate cold rolling gauge)
during an intermediate cold rolling step, which can also comprise
multiple passes. Depending on the hot rolling gauge, desirable
final thickness, and other properties discussed below, an aluminum
alloy may require more or fewer cold rolling passes to achieve the
desired gauge. This number of cold rolling passes is not limited
and can be suitably adjusted, for example, depending on the
desirable thickness of the final sheet and other properties of the
material.
[0026] Following intermediate cold rolling, the process for
producing aluminum alloy fin stock materials comprises an
inter-annealing step to produce desired properties of the aluminum
alloy fin stock material according to the embodiments of the
present invention. The term "inter-annealing" refers to a heat
treatment applied between cold rolling steps. In the context of the
present invention, inter-annealing is applied between the
intermediate and final cold rolling steps. Inter-annealing involves
heating the aluminum alloy to a temperature of about from about 200
to about 400.degree. C., for example, from about 300 to about
375.degree. C., from about 325 to about 350.degree. C., from about
340 to about 360.degree. C., from about 290 to about 360.degree. C.
or from about 345 to about 350.degree. C. ("inter-annealing
temperature"), and maintaining the inter-annealing temperature for
3-5 hours, for example, for about 4 hours, followed by cooling. The
period of maintaining a temperature of about 200 to about
400.degree. C. can also be referred to as "soak" or "soaking " For
heating and cooling the material before and after the soak, a
constant rate of 40 to 50.degree. C./hr, for example, 50.degree.
C./hr, is applied. Inter-annealing conditions affect the structure
and the properties of the aluminum alloy fin stock material in
various ways. For example, higher inter-annealing temperatures can
lead to lower post-braze strength. Accordingly, the inter-annealing
conditions are selected within the ranges specified in this
document to result in the desirable properties of the aluminum
alloy fin stock material.
[0027] Following inter-annealing, final cold rolling is performed
to achieve % cold work (% CW) during the final cold rolling step
(which can comprise multiple cold rolling passes) of 20 to 45%, 25
to 40% , 20 to 40%, 20 to 35%, 25 to 35%, wherein
% C W = thickness before cold rolling - thickness after cold
rolling thickness before cold rolling * 100 % . ##EQU00001##
[0028] After the final cold rolling steps, the aluminum alloy fin
stock material of the present invention possesses a thickness
(gauge) of about 70-100 .mu.m, 70-90 .mu.m, 75-85 .mu.m, or 77-83
.mu.m.
[0029] The final cold rolling step affects the structure and
properties of the aluminum alloy fin stock material. For example,
as % CW increases, pre-braze strength (ultimate tensile strength
(UTS), yield strength (YS), or both, measured in pre-brazed
condition) of the aluminum material increases. Accordingly, the %
CW employed is adjusted within the ranges specified in this
document to achieve desirable properties of the aluminum alloy fin
stock material.
[0030] The processes of producing aluminum alloy fin stock
materials of the present invention lead to an aluminum material
that can be described as "strain-hardened," "cold-worked," and/or
having or being in "H1X" temper (for example, H14 temper). In some
examples, improved fin stock aluminum alloy material according to
the embodiments in the present invention can be produced in H14,
H16 or H18 tempers. It is to be understood that a particular range
of properties is associated with the temper designation. It is also
to be understood that the temper designation refers to the
pre-braze properties of the material.
Properties
[0031] The aluminum alloy fin stock material according to the
embodiments of the present invention possesses a number of
advantageous properties, characteristics or parameters. These
properties, separately or in various combinations, allow the
aluminum alloy materials described in this document to be used in
production of fins for heat exchangers. However, it is to be
understood that the scope of the present invention is not limited
to specific uses or applications, and the properties of the
aluminum alloy fin stock materials can be advantageous for various
other applications. Some of these properties are discussed below.
Some other properties may not be specifically described, but may
follow from the composition of and/or production processes employed
for fabrication of the aluminum alloy fin stock material of the
present invention.
[0032] Some embodiments of the aluminum alloy materials of the
present invention are manufactured as sheets, for example, as
sheets 77-83 .mu.m thick. The aluminum alloy sheets can be produced
in H1X temper (for example, H14 H16 or H18 temper). Aluminum alloy
materials according to the embodiments of the present invention are
manufactured can possess one or more of the following properties,
in any combination: UTS of 210 MPa or more (in other words, at
least 210 MPa) or 210-220 MPa, measured in pre-brazed condition;
UTS of 150 MPa or more (in other words, at least 150 MPa) or
150-160 MPa, measured post-brazing; sag resistance of 25-33 mm
measured post-brazing; conductivity of 42-48, 43-47, or 44-45 IACS
measured post-brazing; open circuit potential corrosion value (vs.
Standard Calomel Electrode (SCE), also referred to as "corrosion
potential") of -740 mV or less (for example, -750 mV); and/or
coarse post-braze grain microstructure. The parameters measured
"after brazing" or "post-brazing," also referred to as
"post-braze," are measured after a simulated brazing cycle, during
which aluminum alloy samples are heated to a temperature of 595 to
610.degree. C. and cooled to room temperature in a period of about
20 minutes. The parameters measured before brazing ("pre-brazing"
or in "pre-brazed" condition), also referred to as "pre-braze"
parameters are measured before or without subjecting the material
to any brazing cycle.
[0033] Some embodiments of aluminum alloy fin stock material of the
present invention have improved strength and conductivity and
exhibit lower corrosion potential values. The term "conductivity"
and the related terms and expressions used herein to describe
aluminum alloy fin stock material of the present invention may
refer to thermal (heat) conductivity or electrical conductivity,
depending on the context. When not explicitly defined, the term
"conductivity" generally, but not always, refers to electrical
conductivity. Conductivity expressed in IACS units is electrical
conductivity. The above properties and advantages allow aluminum
alloy fin stock material of the present invention to be
advantageously employed in various uses and applications, discussed
in more detail below.
Uses and Applications
[0034] The aluminum alloy fin stock materials described in this
document can be used in various applications, for example, but not
limited to, heat exchangers. In one embodiment, the aluminum alloy
fin stock material can be used in automotive heat exchangers such
as radiators, condensers and evaporators. However, the uses and
applications of the improved aluminum alloy fin stock material of
the present invention are not limited to automotive heat exchangers
and other uses are envisioned. For example, the improved aluminum
alloy fin stock material of the present invention can be used for
manufacture of various devices employing heat exchangers and
produced by brazing, such as devices employed in heating,
ventilation, and air conditioning (HVAC). Uses and applications of
the aluminum alloy fin stock materials described herein are
included within the scope of the present invention, as are objects,
forms, apparatuses and similar things fabricated with or comprising
the aluminum alloys described herein. The processes for
fabricating, producing or manufacturing such objects, forms,
apparatuses and similar things are also included within the scope
of the present invention.
[0035] Aluminum alloys described herein are suitable for
fabrication or manufacturing processes that require the joining of
metal surfaces by brazing. Brazing is a metal joining process in
which filler metal is heated above a melting point and distributed
between two or more close-fitting parts by capillary action. The
uses of the aluminum alloys in brazing and the related processes
and results, such as the objects fabricated according to the
manufacturing process that involve brazing, are generally referred
to as "brazing applications." The parts of the heat exchangers
according to some of the embodiments of the present invention are
joined by brazing during the manufacturing process. During brazing,
the filler metal melts and becomes the filler metal that is
available to flow by capillary action to points of contact between
the components being brazed.
[0036] One exemplary object that can be fabricated using aluminum
alloy fin stock materials described herein is a heat exchanger.
Heat exchangers are produced by the assembly of parts comprising
tubes, plates, fins, headers, and side supports to name a few. For
example, a radiator is built from tubes, fins, headers and side
supports. Except for the fins, which are typically bare, meaning
not clad with an Al-Si alloy, all other parts of a heat exchanger
are typically clad with a brazing cladding on one or two sides.
Once assembled, a heat exchanger unit is secured by banding or such
device to hold the unit together through fluxing and brazing.
Brazing is commonly effected by passing the unit through a tunnel
furnace. Brazing can also be performed by dipping in molten salt or
in a batch or semi-batch process. The unit is heated to a brazing
temperature between 590.degree. C. and 610.degree. C., soaked at an
appropriate temperature until joints are created by capillary
action and then cooled below the solidus of the filler metal.
Heating rate is dependent on the furnace type and the size of the
heat exchanger produced. Some other examples of the objects that
can be fabricated using aluminum alloy fin stock materials
described herein are an evaporator, a radiator, a heater or a
condenser.
[0037] The following example will serve to further illustrate the
present invention without, at the same time, however, constituting
any limitation thereof. On the contrary, it is to be clearly
understood that resort may be had to various embodiments,
modifications and equivalents thereof which, after reading the
description herein, may suggest themselves to those skilled in the
art without departing from the spirit of the invention.
EXAMPLE 1
[0038] An aluminum alloy comprising 1.0-1.1 wt. % Si, 0.37-0.42 wt.
% Fe; 1.5-1.6 wt. % Zn, 1.3-1.35 wt. % Mn, 0.27-0.33 wt. % Cu,
0.04-0.05 wt. % Mg, with the remainder being aluminum and
unavoidable impurities, was DC cast into an ingot. The ingot was
preheated to 480.degree. C. in 12 hours at a heating rate of
50.degree. C./hr, soaked at 460-480.degree. C. for 6 hours and hot
rolled to 3.5-4 mm thickness. Next the sheet was cold rolled to
about 1 mm thickness and then cold rolled to about 123 .mu.m
intermediate thickness, followed by an inter-annealing treatment
involving a soak at 350.degree. C. for 4 hours, with constant
heating and cooling rate of 50.degree. C./hr applied before and
after the soak, and subsequent cold rolling to a final gauge of
about 80 .mu.m, which corresponds to 35% CW. The resulting alloy
material had a minimum ultimate tensile strength of about 220 MPa
in pre-braze condition and about 150-160 MPa post-brazing. The
alloy material had an average conductivity post-brazing of about
44-45 IACS and an open circuit potential corrosion value (vs.
Standard Calomel Electrode (SCE)) of -750 mV measured per the ASTM
G69 standard. The alloy material exhibited a coarse post-braze
microstructure and a sag value of 21.5 mm (an average of 2
measurements using different coupons from the same sample). The
above properties were measured after applying a simulated brazing
cycle, during which the samples were heated to a temperature of
605.degree. C. and cooled to room temperature in a period of about
20 minutes, to simulate the temperature time profile of a
commercial brazing process.
EXAMPLE 2
[0039] An aluminum alloy comprising 1.0-1.1 wt. % Si, 0.37-0.42 wt.
% Fe; 1.5-1.6 wt. % Zn, 1.3-1.35 wt. % Mn, 0.27-0.33 wt. % Cu,
0.04-0.05 wt. % Mg, with the remainder being aluminum and
unavoidable impurities, was DC cast into an ingot. The ingot was
preheated to 480.degree. C. in 12 hours at a heating rate of
50.degree. C./hr, soaked at 460-480.degree. C. for 6 hours and hot
rolled to 3.5-4 mm thickness. Next the sheet was cold rolled to
about 1 mm thickness and then cold rolled to an intermediate
thickness, followed by inter-annealing treatment at two different
temperatures. For inter-annealing, the samples of the alloy were
subjected to soaks at either 350.degree. C. or 500.degree. C. for 4
hours, with a constant heating and cooling rate of 50.degree. C./hr
applied before and after the soak, and subsequent cold rolling to a
final gauge of about 80 .mu.m, corresponding to 40% CW. The sag
resistance values and post-braze microstructure of the alloy
samples were examined after applying a simulated brazing cycle
described in Example 1. The alloy samples ("first group") produced
with inter-annealing involving a soak at 350.degree. C. exhibited a
coarse post-braze microstructure and an average sag value of 24 mm.
In comparison, the alloy samples produced with inter-annealing
involving a soak at 500.degree. C. ("second group") exhibited a
finer post-braze grain structure than the first group and an
average sag value of 32 mm. The alloy samples of the first group,
annealed at lower temperature, exhibited higher sag resistance
values.
[0040] All patents, patent applications, publications, and
abstracts cited above are incorporated herein by reference in their
entirety. Various embodiments of the invention have been described
in fulfillment of the various objectives of the invention. It
should be recognized that these embodiments are merely illustrative
of the principles of the present invention. Numerous modifications
and adaptations thereof will be readily apparent to those of skill
in the art without departing from the spirit and scope of the
invention as defined in the following claims.
* * * * *