U.S. patent application number 11/334774 was filed with the patent office on 2006-08-10 for aluminium alloy brazing material.
This patent application is currently assigned to Corus Aluminium Walzprodukte GmbH. Invention is credited to Steven Dirk Meijers.
Application Number | 20060177688 11/334774 |
Document ID | / |
Family ID | 36780322 |
Filed Date | 2006-08-10 |
United States Patent
Application |
20060177688 |
Kind Code |
A1 |
Meijers; Steven Dirk |
August 10, 2006 |
Aluminium alloy brazing material
Abstract
Disclosed is an aluminium alloy brazing material which is
substantially lithium-free and calcium-free, and has the
composition, in weight percent: Si 5.0 to 14.0; Fe 0.1 to 0.7; Mn
0.2 to 1.5; Mg max. 2.0; Zn max 1.0; optionally a wetting agent as
alloying element up to 1%, and balance Al and inevitable
impurities.
Inventors: |
Meijers; Steven Dirk; (Me
Alkmaar, NL) |
Correspondence
Address: |
STEVENS DAVIS MILLER & MOSHER, LLP
1615 L STREET, NW
SUITE 850
WASHINGTON
DC
20036
US
|
Assignee: |
Corus Aluminium Walzprodukte
GmbH
Koblenz
DE
|
Family ID: |
36780322 |
Appl. No.: |
11/334774 |
Filed: |
January 19, 2006 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60649582 |
Feb 4, 2005 |
|
|
|
Current U.S.
Class: |
428/654 ;
420/548 |
Current CPC
Class: |
B23K 35/0233 20130101;
B23K 2101/14 20180801; Y10T 428/12764 20150115; C22C 21/02
20130101; B23K 35/286 20130101; B23K 2103/10 20180801 |
Class at
Publication: |
428/654 ;
420/548 |
International
Class: |
C22C 21/02 20060101
C22C021/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 22, 2005 |
EP |
05076694.8 |
Feb 4, 2005 |
EP |
05075292.2 |
Claims
1. An aluminium alloy brazing material which is substantially
lithium-free and calcium-free, and comprising the composition, in
wt. %: TABLE-US-00003 Si 5.0 to 14.0 Fe 0.1 to 0.7 Mn 0.2 to 1.5 Mg
max. 2.0 Zn max 1.0, and
optionally a wetting agent as alloying element of at most 1%, the
balance Al and inevitable impurities.
2. An aluminium alloy brazing material according to claim 1,
wherein the alloy Mn/Fe ratio in weight percent is at least
1/1.
3. An aluminium alloy brazing material according to claim 1,
wherein the alloy Mn/Fe ratio in weight percent is at least
2/1.
4. An aluminium alloy brazing material according to claim 1, having
an intermetallic phase containing Mn and Fe in a ratio of Mn/Fe in
weight percent of at least 0.4/1.
5. An aluminium alloy brazing material according to claim 1, having
an intermetallic phase containing Mn and Fe in a ratio of Mn/Fe in
weight percent of at least 0.5/1.
6. An aluminium alloy brazing material according to claim 1, having
an intermetallic phase containing Mn and Fe in a ratio of Mn/Fe in
weight percent of at least 0.7/1.
7. An aluminium alloy brazing material according to claim 1,
wherein the Si-content is in a range of 7.0 to 12.0%.
8. An aluminium alloy brazing material according to claim 1,
wherein the Mn-content is in a range of 0.3 to 1.0%.
9. An aluminium alloy brazing material according to claim 1,
wherein the Mn-content is in a range of 0.4 to 1.0%.
10. An aluminium alloy brazing material according to claim 1,
wherein the Mn-content is in a range of 0.4 to 0.8%.
11. An aluminium alloy brazing material according to claim 1,
wherein the Mg-content is in a range of up to 1%.
12. An aluminium alloy brazing material according to claim 1,
wherein the Mg-content is in a range of up to 0.4%.
13. An aluminium alloy brazing material according to claim 1,
wherein the Zn-content is in a range of up to 0.5%.
14. An aluminium alloy brazing material according to claim 1,
wherein the Fe-content is in the range of 0.1 to 0.6%.
15. An aluminium alloy brazing material according to claim 1,
wherein the Fe-content is in the range of 0.2 to 0.6%.
16. An aluminium alloy brazing material according to claim 1,
wherein a wetting agent as alloying element is present in a range
of up to 0.8%.
17. An aluminium alloy brazing material according to claim 1,
wherein the wetting agent is selected from the group consisting of
lead, bismuth, antimony, tin, silver, thallium, indium, and any
mixture thereof.
18. An aluminium alloy brazing material according to claim 1,
wherein the material is substantially sodium-free.
19. An aluminium alloy brazing material according to claim 1,
wherein the material is substantially beryllium-free.
20. A member suitable for brazing having a base of aluminium or
aluminium alloy and a clad layer on said base having a lower
melting point than said base, wherein said clad layer is an
aluminium alloy brazing material according to claim 1.
21. A brazed assembly comprising at least two members joined by an
aluminium alloy brazing material according to claim 1.
22. A brazed assembly according to claim 21, wherein the brazing
material is in the form of a clad layer on one of said members or a
fillet joining said two members.
23. An aluminium alloy brazing material which is substantially
lithium-free and calcium-free, and comprising the composition, in
wt. %: TABLE-US-00004 Si 5.0 to 14.0 Fe 0.1 to 0.7 Mn 0.2 to 1.5 Mg
max. 2.0 Zn max 1.0, and
the balance Al and inevitable impurities.
24. An aluminium alloy brazing material according to claim 1,
further comprising a wetting agent as alloying element of at most
1%.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This claims the benefit of U.S. provisional patent
application No. 60/649,582 filed Feb. 4, 2005, European patent
application number 05075292.2 filed Feb. 4, 2005 and European
patent application number 05076694.8 filed Jul. 22, 2005, all of
which are incorporated herein by reference in their entirety.
FIELD OF THE INVENTION
[0002] This invention relates to aluminium alloy brazing material
which is substantially lithium-free and calcium-free, and to a
brazed assembly including, as a joining material, a resolidified
aluminium alloy brazing material.
BACKGROUND OF THE INVENTION
[0003] Brazing is commonly used to assemble a complex structure,
such as a heat exchanger, made of aluminium or aluminium alloy
components. Generally, a clad layer of brazing material is provided
on at least one component, and forms a fillet of resolidified
material joining two components, following brazing. Alternatively,
a fillet of aluminium alloy brazing material is added to the
structure before brazing, to form a joining fillet of resolidified
material in the brazed product. In recent years, there has been
much improvement in the corrosion resistance of aluminium alloy
sheets and tubes used in such structures. As a result, the present
inventors have perceived that the corrosion resistance performance
of the structure may become determined by the corrosion resistance
of the fillet, rather than by the corrosion resistance of the base
materials.
[0004] There is little in the literature describing study of
corrosion of the resolidified clad or fillet. In unpublished work,
we have found that (i) the addition of Zn to the clad material is
ineffective to improve corrosion resistance of the brazed product
(somewhat contradicting some published work mentioned below) and
(ii) adding Cu to the clad decreased the corrosion resistance of
the tube to which the clad was applied (the reason for this is
believed to be that the beneficial potential difference between
diffusion zone and clad disappears, which results in poor core
corrosion performance).
[0005] Clad materials typically have a high Si content, for example
10 wt %. In one published study, Chen, Wu & Li, "The effects of
trace elements on Al--Si alloys brazing filler metal", Hanjie
Xuebao (1985) vol. 6, no. 2, pp. 55 (in Chinese), small additions
of Na, Sr, La or Ce improved the corrosion behaviour, while Bi made
it worse. This was measured by comparing the strength of the joint
before and after corrosion testing. Kuroda & Tohma,
"Electrochemical properties of Al--Si brazing filler, Aluminium
Alloys--Their physical and mechanical properties", Proceedings of
the 6.sup.th International Conference on Aluminium Alloys, ICAA-6,
Japan, 1998, pp. 1543, report the effects of alloy elements in the
clad (filler) alloy on the corrosion behaviour of the filler
material. The effect of Si, Zn and Cu was studied. Corrosion was
found preferentially in the eutectic phase. The conclusion reached
was that a clad (filler) alloy containing a large amount of Zn may
give better performance against pitting of the core. Similarly
Takemoto, Okamoto & Kurishima, "Sacrificial anode type
Al-10Si-1Mg brazing filler metals for suppression of corrosion of
brazed 3003 aluminium alloy", Transactions of JWRI (1986), vol. 15,
no. 2, pp. 111, added 0.5% Fe to a filler containing 10% Si, 1% Mg
and different levels of Zn or Sn, to study the corrosion behaviour
of the AA3003 core alloy. No effect of Fe was found, while Zn and
Sn improved the corrosion performance of the core alloy. The same
authors Takemoto & Okamoto, "Effect of iron content in brazing
filler metals on corrosion of brazed aluminium", Transactions of
JWRI (1986), vol. 15, no. 2, pp. 101, have reported no effect of
the iron content, up to 1.4 wt %, in the 10 wt % Si filler alloy on
the corrosion behaviour of AA3003 or pure aluminium. A slight
effect was found on AA1100.
[0006] Outside the field of brazing materials, there have been
studies on the corrosion behaviour of precipitates or intermetallic
compounds, which are often found in AA3xxx type alloys. These
precipitates are typically Al (Mn, Fe) Si and Al (Mn, Fe), the iron
being usually present as an impurity in commercial alloys.
Nisancioglu & Lunder, "Significance of the electrochemistry of
Al-base intermetallics in determining the corrosion behaviour of
aluminium alloys", Aluminium Alloys--Physical and mechanical
properties, Charlottesville USA (1986), pp. 1125, discuss these
questions, and show that Mn has an effect to reduce the corrosion
potential of the AlMnFe phase. It was also shown that, in alloys
with 0.7 wt % Fe, Si levels up to 0.3% proved to be beneficial.
[0007] Zamin, "The role of Mn in the corrosion behaviour of Al--Mn
alloys", Corrosion (1981), vol. 37, no. 11, pp. 627, studied the
corrosion behaviour of laboratory-cast Al--Mn alloys, and found
that the corrosion behaviour improves with the increasing Mn/Fe
ratio. A similar effect was shown by Fukuzuka, Shimogori &
Fujiwara, "Relationship between the initiation of microscopic
pitting corrosion and the composition of the Al6Mn.sub.xFe.sub.1-x
intermetallic compounds in aluminium-manganese alloys", Boshoku
Gijutsu (1979) vol. 28, pp. 323 (in Japanese).
[0008] In the light of the disclosure of the invention below,
attention is also drawn to U.S. Pat. No. 4,648,918, which describes
an abrasion resistant aluminium alloy which is used for the
production of mechanical parts by extrusion and has a content of
7.5 to 15 wt % of Si, 3.0 to 6.0 wt % of Cu, 0.3 to 1.0 wt % of Mg,
0.25 to 1.0 wt % of Fe and 0.25 to 1.0 wt % of Mn, balance Al and
impurities. Secondly, mention is made of U.S. Pat. No. 4,854,495,
which discloses, in the production of electronic components and
semiconductor components where soldering of ceramic and metal is
desired, the use of a high-melting jointing material comprising a
core material comprised of aluminium-1.3% manganese alloy with a
skin layer comprised of aluminium-10% silicon-2% manganese
alloy.
SUMMARY OF THE INVENTION
[0009] The object of the present invention is to provide aluminium
alloy brazing material having improved corrosion resistance of the
resolidified clad or fillet in the brazed structure, bearing in
mind that in a commercially produced alloy, iron is inevitably to
be found.
[0010] According to the present invention there is provided an
aluminium alloy brazing material which is substantially
lithium-free and calcium-free, and comprising the composition, in
weight percent: TABLE-US-00001 Si 5.0 to 14.0, preferably 7.0-12.0
Fe 0.1-0.7, preferably 0.2-0.6 Mn 0.2-1.5, preferably 0.3-1.0, more
preferably 0.4-0.8 Mg max. 2.0 Zn max. 1.0, and
[0011] optionally a wetting agent as alloying element up to 1 wt.
%, and
[0012] balance Al and inevitable impurities.
BRIEF DESCRIPTION OF THE DRAWING
[0013] FIG. 1 is the sole figure and shows a brazed structure.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0014] The invention is based on the finding that, in a brazing
material, for example a clad or filler layer, containing a high Si
content, Mn can play a significant role in improving the corrosion
performance of the resolidified brazing material in a brazed
product.
[0015] The term "substantially free" means having no significant
amount of that component purposely added to the alloy composition,
e.g. at a level of <0.005% and more preferably absent, it being
understood that trace amounts of incidental elements and/or
impurities may find their way into a desired end product.
[0016] Particularly it is preferred that the Mn/Fe ratio in weight
percent is at least 1, preferably at least 2 weight percent. It is
also believed to be desirable to select the amount of Mn such that,
in an intermetallic phase in the resolidified brazing material
containing Mn and Fe, the ratio of Mn/Fe in weight percent is at
least 0.4, preferably at least 0.5, more preferably at least 0.7
weight percent. All percent compositions given in this
specification are weight percents unless otherwise indicated.
[0017] The invention further provides a product suitable for
brazing, having a base (core) of aluminium or aluminium alloy and a
clad layer on said base having a lower melting point than said
base, wherein the clad layer is aluminium alloy brazing material of
the invention as described above.
[0018] The invention further provides a brazed assembly comprising
at least two members joined by an aluminium alloy brazing material
of the invention as set out above. Typically this brazing material
is in the form of a clad layer on one of the members or a fillet
joining the two members.
[0019] In the aluminium alloy brazing material of the invention,
the amount of Si is selected in a conventional manner, to provide
the desired brazing properties of the alloy.
[0020] The amount of Fe depends primarily on the origin of the
alloy material.
[0021] The amount of Mn is in the range 0.2 to 1.5%, because below
0.2% the effect of improved corrosion resistance is not found.
Preferably the amount of Mn is at least 0.3%, and more preferably
at least 0.4%, to provide improved corrosion resistance. With a
view to the properties of the alloy, the amount of Mn should be not
more than 1.5%, preferably not more than 1.0%. The preferred
maximum is 0.8%, since above this level the improved corrosion
resistance may be less.
[0022] The amount of Mg is chosen in accordance with the intended
type of brazing of the particular product. For CAB brazing, a
relatively low level of Mg may be present, e.g. up to 0.4%. For
vacuum brazing, a higher level, up to 2.0% preferably not more than
1%, is suitable.
[0023] Zn is an impurity element which can be tolerated to a level
of up to 1%, and is preferably not more than 0.5%.
[0024] The brazing material comprises optionally a wetting agent as
alloying element in a range of up to 1 wt. %, and preferably up to
0.8 wt. % in order to improve the wettability of the brazing
material during the brazing process, in particular during vacuum
brazing or controlled atmosphere brazing (CAB) in the absence of a
brazing flux material. Preferably the wetting agent is selected
from the group consisting of lead, bismuth, antimony, tin, silver,
thallium, indium, and any mixture thereof.
[0025] The balance of the composition is aluminium and inevitable
impurities, and preferably maximum impurities in total preferably
0.20 wt %, with no element more than 0.05 wt %.
[0026] Preferred embodiments of this aluminium alloy are also
substantially sodium-free and beryllium-free.
EXAMPLES
[0027] The invention will now be illustrated by non-limitative
examples.
[0028] For the purposes of study, seven alloys suitable for the use
as brazing filler materials (clad or fillet) were cast, having the
compositions given in Table 1. Alloys 1, 2 and 3 are comparative,
and have an increasing amount of Fe without Mn. Alloys 4, 5, 6 and
7 have an increasing amount of Mn, with constant Fe. TABLE-US-00002
TABLE 1 Amounts in wt. %, balance is aluminium plus inevitable
impurities. Melting Alloy Temperature No. Mn Fe Si Mg (.degree. C.)
1 <0.01 0.06 10.2 0.03 578.2 2 <0.01 0.26 10.2 0.03 577.6 3
<0.01 0.52 10.1 0.03 576.8 4 0.21 0.28 10.1 0.03 579.0 5 0.42
0.28 10.2 0.03 578.6 6 0.49 0.27 10.0 0.03 579.1 7 0.81 0.28 10.1
0.03 579.5
[0029] Just before casting, 1 kg/ton AlTiB5/1 was added as a grain
refiner.
[0030] DSC (Differential Scanning Calometry, also known as
Differential Scanning Calorimetry) was used to determine the
melting temperature (onset of melting) of the alloys, since the
effect of Mn on the melting point was not known. The melting points
show that the melting temperature will not affect the brazing
properties of these alloys.
[0031] These filler alloys were used to form fillets in a brazed
structure, shown in FIG. 1, in which the sheet 1 and the angular
coupon 2 are AA3003 aluminium alloy. The brazing alloy forms the
fillet 3. In each sample about 85 mg filler alloy was used, and the
samples were brazed using 2 g/m.sup.2 flux.
[0032] Corrosion tests were performed on both the filler alloys as
cast, and on the brazed fillets. Polished samples were exposed to a
NaCl solution (3%, twice for 90 minutes) light microscopy pictures
were taken before and after corrision the same location. Corrosion
was qualitatively established from the visible local attack around
second phase particles. For the alloys as cast, it was found that
the corrosion performance deteriorates with increasing Fe content,
for alloys 1, 2 and 3. On the other hand, the corrosion attack
clearly decreased with increasing Mn content in the alloys 4, 5 and
7. The corrosion performance of alloy 6 was similar to that of
alloy 5.
[0033] Similarly, using light microscopy images, corrosion was
inspected for the fillets of the brazed product shown in FIG. 1.
Corrosion after 90 and 180 minutes exposure in 3% NaCl was studied.
While there was not much difference between the corrosion attack on
alloys 1 and 2, there was much more corrosion for alloy 3. All four
of alloys 4, 5, 6 and 7 showed improved corrosion resistance,
compared with the fillet of alloy 2. The optimum effect was
achieved for alloys 5 and 6, with alloy 7 showing a less good
performance than alloys 5 and 6.
[0034] From these results, improved corrosion resistance is
expected for the brazing material of the invention, when used as a
clad layer as a member on an aluminium or aluminium alloy base
(core) in a construction subjected to brazing, with
resolidification of the material of the clad layer. The brazing
material of the invention can be applied for example to
constructions such as heat exchangers.
[0035] Having now fully described the invention, it will be
apparent to one of ordinary skill in the art that many changes and
modifications can be made without departing from the spirit or
scope of the invention as herein described.
* * * * *