U.S. patent application number 10/596060 was filed with the patent office on 2007-05-03 for aluminium alloy strip for brazing.
This patent application is currently assigned to Alcan Rhenalu. Invention is credited to Sandrine Dulac, Sylvain Henry.
Application Number | 20070099023 10/596060 |
Document ID | / |
Family ID | 34566233 |
Filed Date | 2007-05-03 |
United States Patent
Application |
20070099023 |
Kind Code |
A1 |
Dulac; Sandrine ; et
al. |
May 3, 2007 |
Aluminium alloy strip for brazing
Abstract
The invention relates to a strip or sheet of aluminium alloy,
comprising at least 80% by weight of aluminium and 0.01 to 0.5%
yttrium and/or 0.05 to 0.5% bismuth, coated on at least one face
with a brazing alloy. Said sheets and strips are used for the
production of pieces by non-flux brazing.
Inventors: |
Dulac; Sandrine; (Grenoble,
FR) ; Henry; Sylvain; (Saint Jean de Moirans,
FR) |
Correspondence
Address: |
BANNER & WITCOFF, LTD.
TEN SOUTH WACKER DRIVE
SUITE 3000
CHICAGO
IL
60606
US
|
Assignee: |
Alcan Rhenalu
Paris
FR
|
Family ID: |
34566233 |
Appl. No.: |
10/596060 |
Filed: |
November 24, 2004 |
PCT Filed: |
November 24, 2004 |
PCT NO: |
PCT/FR04/03003 |
371 Date: |
May 26, 2006 |
Current U.S.
Class: |
428/654 ;
428/650 |
Current CPC
Class: |
B23K 2101/14 20180801;
B23K 1/008 20130101; B23K 2103/10 20180801; B23K 35/0238 20130101;
B23K 1/0012 20130101; B32B 15/016 20130101; B23K 35/002 20130101;
B23K 35/286 20130101; C23C 30/00 20130101; Y10T 428/12764 20150115;
C22C 21/00 20130101; B23K 35/3613 20130101; Y10T 428/12736
20150115 |
Class at
Publication: |
428/654 ;
428/650 |
International
Class: |
B32B 15/01 20060101
B32B015/01 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 28, 2003 |
FR |
0314001 |
Claims
1. Aluminum core alloy strip or sheet containing at least 80% by
weight of aluminum, 0.01 to 0.5% of yttrium and/or 0.05 to 0.5% of
bismuth, and the following elements included in the following
percentages by weight: Si<1.0; Fe<1.0; Cu<1.0; Mn<2.0;
Mg<3.0; Zn<6.0; Ti<0.3; Zr<0.3; Cr<0.3; Hf<0.6;
V<0.3; Ni<2.0; Co<2.0; In<0.3; Sn<0.3; other
elements<0.05 each and 0.15 total, the strip or sheet being
coated on at least one face with a brazing aluminum alloy.
2. Strip or sheet according to claim 1, characterized in that the
brazing alloy is an alloy containing 4 to 15% by weight of
silicon.
3. Strip or sheet according to claim 1, characterized in that the
brazing alloy contains at least one element for modifying the
surface tension of the alloy, the element selected from the group
consisting of Ag, Be, Bi, Ce, La, Pb, Pd, Sb, Y or mischmetal.
4. Strip or sheet according to claim 1, characterized in that the
brazing alloy coating is a clad layer obtained by co-rolling with
the basic aluminum alloy.
5. Strip or sheet according to claim 1, characterized in that the
brazing alloy coating includes one or more particles.
6. Brazed part made using an aluminum alloy strip or sheet
containing 0.01 to 0.5% of yttrium and/or 0.05 to 0.5% of bismuth,
and the following elements included in the following percentages by
weight: Si<1.0; Fe<1.0; Cu<1.0; Mn<2.0; Mg<3.0;
Zn<6.0; Ti<0.3; Zr<0.3; Cr<0.3; Hf<0.6; V<0.3;
Ni<2.0; Co<2.0; In<0.3; Sn<0.3; other elements<0.05
each and 0.15 total.
7. Brazed part according to claim 6, characterized in that the
strip or sheet used is coated with a brazing alloy.
8. Brazed part according to claim 7, characterized in that the
strip or sheet used is coated with brazing alloy particles.
9. Strip or sheet according to claim 5, wherein the particles
comprise a resin layer.
10. Brazed part according to claim 8, wherein the brazing alloy
particles are coated by a polymer resin.
11. An aluminum alloy component for the assembly of parts by
fluxless brazing comprising at least about 80% by weight of
aluminum, and 0.01 to 0.5% of yttrium and/or 0.05 to 0.5% of
bismuth, wherein at least one face of the aluminum alloy component
is coated with a brazing alloy.
12. The aluminum alloy component according to claim 11, wherein the
brazing alloy is an alloy containing 4 to 15% by weight of
silicon.
13. The aluminum alloy component according to claim 11, wherein the
brazing alloy contains at least one element for modifying the
surface tension of the alloy, the element selected from the group
consisting of Ag, Be, Bi, Ce, La, Pb, Pd, Sb, Y or mischmetal.
14. The aluminum alloy component according to claim 11, wherein the
brazing alloy coating is a clad layer obtained by co-rolling with
the basic aluminum alloy.
15. The aluminum alloy component according to claim 11,
characterized in that the brazing alloy coating includes one or
more particles.
16. The aluminum alloy component according to claim 15, wherein the
particles comprise a resin layer coating the aluminum alloy
component.
17. The aluminum alloy component according to claim 11, wherein the
component includes the following elements in the following
percentages by weight: Si<1.0; Fe<1.0; Cu<1.0; Mn<2.0;
Mg<3.0; Zn<6.0; Ti<0.3; Zr<0.3; Cr<0.3; Hf<0.6;
V<0.3; Ni<2.0; Co<2.0; In<0.3; Sn<0.3; other
elements<0.05 each and 0.15 total.
Description
FIELD OF THE INVENTION
[0001] The invention relates to aluminium alloy strips, possibly
cladded on one or two faces with a brazing alloy and intended for
the production of brazed parts, particularly heat exchangers for
automobiles or buildings, and more particularly parts assembled by
fluxless brazing under a controlled atmosphere.
STATE OF THE ART
[0002] The most frequently used process for the assembly of
automobile heat exchangers is brazing. This is based on the use of
a cladded strip composed of a so-called "core" alloy coated on one
or two faces with a so-called "brazing" alloy, at least for one of
the components to be assembled. This so-called "brazing" alloy is
characterised by a liquid temperature about 30.degree. C. less than
the solidus temperature of the core alloy. By applying an
appropriate heat treatment, it is possible to melt only the
cladding, which then wets the surfaces in contact allowing good
assembly after the assembly has cooled.
[0003] There are three different brazing techniques presently
available:
[0004] The most widespread is brazing under a controlled nitrogen
atmosphere, after coating parts to be assembled with a
non-corrosive "flux", the most frequently used being the
Nocolok.RTM. flux. This product, designed to dissolve the surface
oxide layer on aluminium and consequently to increase the
wettability of the surfaces, is of the potassium fluoro-aluminate
type. A number of problems arise when it is used. Obviously, the
product has an intrinsic cost; its deposition requires special
installations that frequently prevent complete automation of
exchanger production lines; finally an effluent treatment must be
arranged.
[0005] Another older technique but one still used particularly in
North America is vacuum brazing. This process makes it necessary to
use cladding that contains magnesium; this element is segregated on
the surface and vaporises in the vacuum, capturing residual traces
of oxygen. It thus avoids the oxide layer, initially broken by
differential expansion, from reforming. No flux is necessary, but
vacuum-creating installations are very complicated and associated
maintenance costs are very high. For these economic reasons,
existing lines are progressively being abandoned and replaced by
Nocolok.RTM. lines.
[0006] Finally, a third process used more marginally, consists of
depositing a nickel layer instead of the flux. Brazing is then done
under nitrogen. The energy released during the brazing cycle by the
creation of Al--Ni phases on the cladding surface is sufficient to
break the oxide layer.
[0007] The main problem consists of performing the brazing
operation on existing Nocolok.RTM. lines, since these are the most
widespread and the most economic, without the use of flux or any
other complex surface preparation and without causing degradation
of the final properties of exchangers that will be assembled using
this technique.
[0008] The solution that has been developed most widely in this
field is an adaptation of the nickel deposition brazing process.
Although increasingly simplified deposition techniques have been
found and used, for example as described in patent application WO
02/07928 (Corus), they never provide more than a partial solution
to the problem.
[0009] The manufacturer of exchangers, or of aluminium strips if
the operation is carried out by this manufacturer, must always add
on specific installations for surface preparation before brazing
and must continue to manage effluents, this time generated by
nickel plating baths. Furthermore, although progress has been made
in terms of resistance to corrosion as mentioned in patent
application WO 02/060639 (Corus), the indicated performances do not
always reach the performances claimed for Nocolok.RTM. brazed
products (for example see patent application WO 02/40729 by
Pechiney Rhenalu).
[0010] Other solutions are related to adaptation of the cladding
alloy and/or atmospheric conditions in brazing furnaces, as for
example in U.S. Pat. No. 3,811,177 (VAW) that mentions the addition
of the Bi, Sr, Ba or Sb elements into brazing alloys to modify its
surface tension. The effect of bismuth on the surface tension is
also mentioned in patent EP 0004096 (Ford). More recently, the
advantage of adding sodium, possibly accompanied by potassium or
bismuth, is mentioned in application WO 01/98019 by Kaiser
Aluminium. Finally in EP 1306207 (Sky Aluminium), the brazing that
contains Mg and Bi is covered with a thin layer formed of an
aluminium alloy that will remain solid when it begins to melt; it
will only break later during the brazing cycle, releasing liquid
cladding that then wets its upper surface. Oxidation of the liquid
brazing alloy is avoided by working under an atmosphere for a short
period. The oxide present on the thin layer is broken when it is
surrounded by liquid.
PURPOSE AND OBJECTIVE OF THE INVENTION
[0011] The purpose of the invention is to enable production by
fluxless brazing of parts made of aluminium alloy under good
economic conditions, and particularly using the same equipment as
is used for brazing with flux under a controlled atmosphere.
[0012] The purpose of the invention is an aluminium alloy strip or
sheet containing 0.01 to 0.5% of yttrium and/or 0.05 to 0.5% of
bismuth, coated on at least one face with a brazing alloy. The
coating may be a layer cladded by co-rolling, for example an
aluminium alloy containing 4 to 15% of silicon. It may also be a
layer comprising particles of a brazing alloy, particularly
particles of Al--Si alloy, possibly coated in a resin.
[0013] Another purpose of the invention is a brazed part,
particularly a heat exchanger made using an aluminium alloy strip
or sheet containing 0.01 to 0.5% of yttrium and/or 0.05 to 0.5% of
bismuth.
DESCRIPTION OF THE FIGURES
[0014] FIGS. 1a and 1b show a top and side view respectively of V
test pieces used in the examples to evaluate the brazability.
[0015] FIG. 2 shows the definition of the width of the brazed joint
used in the brazability test described in the examples.
DESCRIPTION OF THE INVENTION
[0016] Unlike the techniques mentioned above, the invention is
designed to modify the composition of the core alloy, such that
brazing can take place without any deposition, under standard
controlled atmosphere conditions, and that can be achieved without
modifying the brazing installations used at equipment
manufacturers.
[0017] Surprisingly, the addition of some elements in the core,
such as yttrium at a content of 0.05% or bismuth at a content of
about 0.15%, can result in a very satisfactory quality of brazed
joints for fluxless brazing under nitrogen.
[0018] The method is applicable to all types of aluminium alloys
containing at least 80% by weight of aluminium, and particularly
alloys for which the composition satisfies the following conditions
(% by weight) before the addition of elements specifically intended
to enable fluxless brazing: [0019] Si<1.0; Fe<1.0; Cu<1.0;
Mn<2.0; Mg<3.0; Zn<6.0; Ti<0.3; Zr<0.3; Cr<0.3;
Hf<0.6; V<0.3; Ni<2.0; Co<2.0; In<0.3; other
elements<0.05 each and 0.15 total; remainder aluminium.
[0020] The sheet or strip may be cladded by co-rolling on one or
two faces with a brazing aluminium alloy, usually an alloy
containing 4 to 15% of silicon. The brazing alloy may contain other
additives such as copper, magnesium or zinc. It may also contain
elements designed to modify the surface tension of the alloy, such
as Ag, Be, Bi, Ce, La, Pb, Pd, Sb, Y or mischmetal, in other words
a mixture of unseparated rare earth metals. In the case in which
the brazing alloy is cladded on a single face, the other face may
be coated by a sacrificial alloy, usually of the Al--Zn type, in a
manner commonly known and intended to improve the resistance of the
core alloy to corrosion.
[0021] The brazing alloy may also be deposited in the form of
particles, particularly Al--Si particles, for example as described
in patent EP 0565568 (Alcan International). For brazing under a
controlled atmosphere, the brazing alloy particles are usually
associated with flux particles, particularly flux based on
fluorides such as potassium fluoro-aluminate, and a binder such as
a polymer resin. One particular advantage of the invention in this
case is to avoid the presence of flux in the coating.
[0022] The alloy sheet with the addition of bismuth and/or yttrium
may also be used uncoated when it is associated with another sheet
coated with a brazing alloy for the production of the brazed
part.
EXAMPLES
Example 1
[0023] Four plates of core alloys with the following compositions
were cast: TABLE-US-00001 ALLOY SI FE CU MN MG TI Y BI CA M 0.40
0.22 0.63 0.57 0.47 0.08 -- -- -- M + Y 0.39 0.24 0.61 0.57 0.47
0.09 0.06 -- -- M + BI 0.39 0.22 0.62 0.59 0.49 0.09 -- 0.15 -- M +
0.40 0.22 0.63 0.57 0.47 0.08 -- -- 0.05 CA
together with a 4047 cladding alloy plate (Al-12% Si). Assemblies
were made from these plates such that the thickness of the cladding
alloy represents 10% of the total thickness. These assemblies were
hot rolled and then cold rolled so as to produce 0.3 mm thick
cladded strips. These strips were then subjected to a restoration
treatment for 10 h at 260.degree. C.
[0024] The test piece illustrated in FIG. 1 was used to evaluate
the brazability of these materials. The "V" is composed of a 0.3 mm
thick bare strip made of a 3003 alloy in the H24 temper. A
15-minute degreasing treatment at 250.degree. C. was applied to the
metal to be brazed. No other surface preparation was used and in
particular no flux was deposited. Brazing is done in a double-wall
glass furnace in which it is possible to view movements of liquid
brazing alloy and the formation of joints during the treatment. The
thermal cycle is composed of a temperature rise phase up to
610.degree. C. at a rate of approximately 20.degree. C./min,
holding for 2 minutes at 610.degree. C., and then lowering at a
rate of about 30.degree. C./minute. The complete process is done
under continuous nitrogen scavenging, at a rate of 8 l/min.
[0025] The results are marked A to E at the following scale:
TABLE-US-00002 Mark A B C D E Joint length formed as a 100% 90% 75%
50% 0% percent of the total length
[0026] The results are given in table 1: TABLE-US-00003 TABLE 1
Core Cladding Brazability M 4047 E M + Y 4047 A M + Bi 4047 A M +
Ca 4047 E
[0027] The improvement in the brazability obtained due to the
addition of Y or Bi to the core alloy can be seen.
Example 2
[0028] Two plates with the following compositions were cast in the
same way: TABLE-US-00004 Alloy Si Fe Cu Mn Mg Ti Y N 0.17 0.18 0.64
1.37 -- 0.08 -- N + Y 0.19 0.17 0.67 1.32 -- 0.09 0.06
together with a 4045 cladding alloy plate (Al-10% Si). The
transformation procedure and the tests carried out are exactly the
same as for example 1.
[0029] The results are given in table 2: TABLE-US-00005 TABLE 2
Core Cladding Brazability N 4045 E N + Y 4045 A
[0030] It can be seen that the addition of yttrium to alloy N
significantly improves the brazability.
Example 3
[0031] Two plates with the following compositions were cast in the
same way: TABLE-US-00006 Alloy Si Fe Cu Mn Mg Ti Y P 0.15 0.35 0.1
0.1 0.8 0.125 -- P + Y 0.15 0.35 0.1 0.1 0.8 0.125 0.06
together with a 4045 cladding alloy plate (Al-10% Si). The
transformation procedure and the tests carried out are exactly the
same as for example 1.
[0032] The results are given in table 3: TABLE-US-00007 TABLE 3
Core Cladding Brazability P 045 E P + Y 4045 A
[0033] It can be seen that the addition of yttrium to alloy P
significantly improves the brazability.
* * * * *