U.S. patent application number 09/986475 was filed with the patent office on 2002-07-04 for composite metal panel.
Invention is credited to Wittebrood, Adrianus Jacobus.
Application Number | 20020086179 09/986475 |
Document ID | / |
Family ID | 26643259 |
Filed Date | 2002-07-04 |
United States Patent
Application |
20020086179 |
Kind Code |
A1 |
Wittebrood, Adrianus
Jacobus |
July 4, 2002 |
Composite metal panel
Abstract
The invention relates to a rigid composite metal panel
comprising at least two metal parallel plates and/or sheets secured
to the peaks and troughs of a corrugated aluminium stiffener sheet
arranged between the parallel plates and/or sheets, wherein the
corrugated aluminium stiffener sheet is an aluminium brazing sheet
product made from an aluminium brazing sheet product including a
core sheet (1) made of an aluminium alloy having on at least one
surface of the core sheet clad, and preferably on both sides, an
aluminium clad layer (2), the aluminium clad layer being made of an
aluminium alloy comprising silicon in an amount in the range of 2
to 18% by weight, preferably 5 to 14%, and a layer (3) comprising
nickel on the outer surface of the aluminium clad layer. The
invention further relates to a method of manufacturing thereof.
Inventors: |
Wittebrood, Adrianus Jacobus;
(Velserbroek, NL) |
Correspondence
Address: |
STEVENS DAVIS MILLER & MOSHER, LLP
1615 L STREET, NW
SUITE 850
WASHINGTON
DC
20036
US
|
Family ID: |
26643259 |
Appl. No.: |
09/986475 |
Filed: |
November 8, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09986475 |
Nov 8, 2001 |
|
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09573980 |
May 19, 2000 |
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Current U.S.
Class: |
428/652 ;
428/654 |
Current CPC
Class: |
E04C 2002/3455 20130101;
Y10T 428/12715 20150115; B23K 35/0238 20130101; B23K 35/286
20130101; Y10T 428/12792 20150115; Y10T 428/24711 20150115; Y10S
428/926 20130101; E04C 2002/3466 20130101; Y10T 428/12771 20150115;
Y10T 428/24694 20150115; Y10T 428/24149 20150115; E04C 2/3405
20130101; E04C 2/326 20130101; Y10T 428/12944 20150115; Y10T
428/24727 20150115; Y10T 428/1291 20150115; E04C 2/08 20130101;
Y10T 428/1275 20150115; Y10T 428/12903 20150115; E04C 2002/3433
20130101; B32B 15/017 20130101; Y10T 428/12778 20150115; Y10T
428/12708 20150115; Y10T 428/12736 20150115; Y10T 428/12764
20150115; Y10S 428/935 20130101; E04C 2002/3472 20130101 |
Class at
Publication: |
428/652 ;
428/654 |
International
Class: |
B32B 015/10 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 10, 2000 |
NL |
1016583 |
Claims
1. A rigid composite metal panel comprising at least two parallel
metal members, selected from the group consisting of metal plate
and metal sheet, secured to the peaks and troughs of a corrugated
aluminium stiffener sheet arranged between said parallel metal
members, wherein the corrugated aluminium stiffener sheet is made
from an aluminium brazing sheet product comprising a core sheet
made of an aluminium alloy having on at least one surface of said
core sheet clad an aluminium alloy clad layer, the aluminium alloy
clad layer being made of an aluminium alloy comprising silicon in
an amount in the range of 2 to 18% by weight, and a layer
comprising nickel on an outer surface of said aluminium alloy clad
layer.
2. A rigid metal composite panel comprising at least two parallel
metal members, selected from the group consisting of metal plate
and metal sheet, secured to aluminium stiffener sheet having a
honeycomb structure arranged between said parallel metal members,
wherein the aluminium stiffener sheet is made from an aluminium
brazing sheet product comprising a core sheet made of an aluminium
alloy having on at least one surface of said core sheet clad an
aluminium alloy clad layer, the aluminium alloy clad layer being
made of an aluminium alloy comprising silicon in an amount in the
range of 2 to 18% by weight and a layer comprising nickel on an
outer surface of said aluminium alloy clad layer.
3. A composite metal panel according to claim 1, wherein the
corrugated aluminium stiffener sheet is in the form of turbulator
sheet.
4. A composite metal panel according to claim 1, wherein the
corrugated aluminium stiffener sheet is a formed sheet having a
plurality of cup-like cavities, which cup-like cavities are aligned
in parallel rows and whereby in alternating parallel rows the
openings of the cup-like cavities are facing opposed
directions.
5. A composite metal panel according to claim 1, wherein said layer
comprising nickel farther comprises bismuth in a range of at most
5% by weight.
6. A composite metal panel according to claim 1, wherein said layer
comprising nickel is essentially lead-free.
7. A composite metal panel according to claim 1, wherein said layer
comprising nickel has a thickness of not more than 2.0 micron.
8. A composite metal panel according to claim 1, wherein said layer
comprising nickel is applied by means of electroplating.
9. A composite metal panel according to claim 5, wherein said layer
comprising nickel is deposited by electroplating both nickel and
bismuth using an aqueous bath comprising a nickel-ion concentration
in a range of 10 to 100 g/l and a bismuth-ion concentration in the
range of 0.01 to 10 g/l.
10. A brazing sheet product according to claim 1, wherein said
aluminium clad layer further comprises magnesium in a range of at
most 8%.
11. A composite metal panel according to claim 1, further
comprising a layer comprising zinc or tin as a bonding layer
between said outer surface of said aluminium clad layer and said
layer comprising nickel.
12. A composite panel according to claim 11, wherein said bonding
layer has a thickness of not more than 1 micron.
13. A composite metal panel according to claim 11, wherein said
bonding layer comprising zinc or tin is applied by a zincate
treatment or a stannate treatment respectively.
14. A composite metal panel according to claim 1, wherein the
corrugated aluminium stiffener sheet is made from said aluminium
brazing sheet product and said aluminium brazing sheet product
comprises: said core sheet made of said aluminium alloy having on
at least one surface of said core sheet clad said aluminium alloy
clad layer, said aluminium alloy clad layer being made of said
aluminium alloy comprising silicon in an amount in the range of 2
to 18% by weight, said layer comprising nickel on the outer surface
of said aluminium alloy clad layer, and a separately deposited
metal layer on one side of said layer comprising nickel, wherein
said separately deposited metal layer comprises a metal such that
taken together said aluminium alloy clad layer and all layers of
the aluminium brazing sheet product exterior thereto form a metal
filler having a liquidus temperature in the range of 490 to
570.degree. C.
15. A composite metal panel according to claim 14, wherein said
layer comprises copper or copper-based alloy.
16. A composite metal panel according to claim 15, wherein said
layer comprises at least 60% by weight copper.
17. A composite metal panel according to claim 14, wherein said
layer has a thickness of not more than 10 micron.
18. A composite metal panel according to claim 1, wherein at least
one of the parallel metal members is made from a metal selected
from the group consisting of aluminium, aluminium alloy, titanium,
plated or coated titanium, bronze, brass, stainless steel, plated
or coated stainless steel, low-carbon steel, plated or coated
low-carbon steel, high-strength steel, and plated or coated
high-strength steel, nickel or nickel alloy.
19. A composite metal panel according to claim 1, wherein the
parallel metal members have been secured or joined to the aluminium
stiffener sheet by brazing.
20. A composite metal panel according to claim 1, wherein said
layer comprising nickel has a thickness of not more than 1.0
micron.
21. A composite panel according to claim 11, wherein said bonding
layer has a thickness of not more than 0.5 micron.
22. A composite metal panel according to claim 1, wherein both
sides of said core sheet are respectively clad by the aluminium
alloy clad layer and the layer comprising nickel on the outer
surface of said aluminium alloy clad layer.
23. A composite metal panel according to claim 1, wherein the
aluminium alloy of the aluminium alloy clad layer comprises silicon
in an amount in the range of 5 to 14% by weight.
24. A composite metal panel according to claim 2, wherein both
sides of said core sheet are respectively clad by the aluminium
alloy clad layer and the layer comprising nickel on the outer
surface of said aluminium alloy clad layer.
25. A composite metal panel according to claim 2, wherein the
aluminium alloy of the aluminium alloy clad layer comprises silicon
in an amount in the range of 5 to 14% by weight.
26. A composite metal panel according to claim 14, wherein both
sides of said core sheet are respectively clad by the aluminium
alloy clad layer and the layer comprising nickel on the outer
surface of said aluminium alloy clad layer.
27. A composite metal panel according to claim 14, wherein the
aluminium alloy of the aluminium alloy clad layer comprises silicon
in an amount in the range of 5 to 14% by weight.
28. A composite metal panel according to claim 14, wherein said
separately deposited metal layer comprises a metal such that taken
together said aluminium alloy clad layer and all layers of the
aluminium brazing sheet product exterior thereto form a metal
filler having a liquidus temperature in the range of 510 to
550.degree. C.
29. A composite metal panel according to claim 1, wherein the
parallel metal members have been secured or joined to the aluminium
stiffener sheet by brazing in the absence of a brazing flux
material.
30. A composite metal panel according to claim 1, wherein the
parallel metal members have been secured or joined to the aluminium
stiffener sheet by a controlled atmosphere brazing process in the
absence of a brazing flux material.
31. A method of manufacturing a rigid composite metal panel,
comprising the steps of: (a) providing parts, the parts comprising
at least two parallel metal members selected from the group
consisting of metal plate and metal sheet, and a corrugated
aluminium stiffener sheet, wherein the corrugated aluminium
stiffener sheet is made from an aluminium brazing sheet product
comprising a core sheet made of an aluminium alloy having on at
least one surface of said core sheet clad an aluminium alloy clad
layer, the aluminium alloy clad layer being made of an aluminium
alloy comprising silicon in an amount in the range of 2 to 18% by
weight, and a layer comprising nickel on an outer surface of said
aluminium alloy clad layer; (b) assembling the parts into an
assembly such that the aluminium stiffener sheet is arranged
between the parallel metal members; (c) joining the assembly into a
rigid composite metal panel by heating the assembly under a vacuum
or in an inert atmosphere in the absence of a brazing-flux material
at elevated temperature of less than 600.degree. C. for a period
long enough for melting and spreading of the molten filler to form
a joint between each parallel metal member and the corrugated
aluminium stiffener sheet; (d) cooling of the joined composite
metal panel.
32. A method of manufacturing a rigid composite metal panel,
comprising the steps of: (a) providing parts, the parts comprising
at least two parallel metal members selected from the group
consisting of metal plate and metal sheet, and an aluminium
stiffener sheet having a honeycomb structure arranged between said
parallel metal members, wherein the aluminium stiffener sheet is
made from an aluminium brazing sheet product comprising a core
sheet made of an aluminium alloy having on at least one surface of
said core sheet clad an aluminium alloy clad layer, the aluminium
alloy clad layer being made of an aluminium alloy comprising
silicon in an amount in the range of 2 to 18% by weight and a layer
comprising nickel on an outer surface of said aluminium alloy clad
layer; (b) assembling the parts into an assembly such that the
aluminium stiffener sheet is arranged between the parallel metal
members; (c) joining the assembly into a rigid composite metal
panel by heating the assembly under a vacuum or in an inert
atmosphere in the absence of a brazing-flux material at elevated
temperature of less than 600.degree. C. for a period long enough
for melting and spreading of the molten filler to form a joint
between each parallel metal member and the corrugated aluminium
stiffener sheet; (d) cooling of the joined composite metal
panel.
33. A method of manufacturing a rigid composite metal panel,
comprising the steps of: (a) providing parts, the parts comprising
at least two parallel metal members selected from the group
consisting of metal plate and metal sheet, and a corrugated
aluminium stiffener sheet, wherein the corrugated aluminium
stiffener sheet is made from an aluminium brazing sheet product and
said aluminium brazing sheet product comprises: a core sheet made
of an aluminium alloy having on at least one surface of said core
sheet clad an aluminium alloy clad layer, said aluminium alloy clad
layer being made of an aluminium alloy comprising silicon in an
amount in the range of 2 to 18% by weight, a layer comprising
nickel on an outer surface of said aluminium alloy clad layer, and
a separately deposited metal layer on one side of said layer
comprising nickel, wherein said separately deposited metal layer
comprises a metal such that taken together said aluminium alloy
clad layer and all layers of the aluminium brazing sheet product
exterior thereto form a metal filler having a liquidus temperature
in the range of 490 to 570.degree. C.; (b) assembling the parts
into an assembly such that the aluminium stiffener sheet is
arranged between the parallel metal members; (c) joining the
assembly into a rigid composite metal panel by heating the assembly
under a vacuum or in an inert atmosphere in the absence of a
brazing-flux material at elevated temperature of less than
600.degree. C. for a period long enough for melting and spreading
of the molten filler to form a joint between each parallel metal
member and the corrugated aluminium stiffener sheet; (d) cooling of
the joined composite metal panel.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a continuation-in-part, claiming priority under 35
U.S.C. Section 120, of U.S. patent application Ser. No. 09/573,980,
filed May 19, 2000, pending, incorporated herein by reference in
its entirety.
FIELD OF THE INVENTION
[0002] The invention is concerned with a composite rigid metal
panel comprising at least two parallel metal plates and/or sheets
secured to a corrugated aluminium stiffener sheet arranged between
the parallel metal plates and/or sheets, and further to a composite
panel comprising two parallel plates and/or sheets secured to
aluminium stiffener sheet having a honeycomb structure. The
invention further relates to a method of manufacturing thereof.
DESCRIPTION OF THE RELATED ART
[0003] Composite metal panels having an interior honeycomb
structure are usually manufactured by means of adhesion bonding,
such as for example disclosed in U.S. Pat. No. 6,054,200. Composite
metal panels having an interior of corrugated sheet such that the
peaks and troughs thereof are bonded to the parallel metal plates
are usually manufactured by means of adhesion bonding or by welding
techniques, such as by laser welding techniques as disclosed in for
example international application WO-00/26020. The stiffness of the
composite metal panel is to a large extent the resultant of the
design of the corrugated sheet or of the honeycomb structure.
[0004] Composite metal panels are being used in load bearing
structures such as for the floor or cargo decks of a ship, tooling
board, floor or wall panels of an aircraft or a land-transportation
vehicle, e.g. a truck or a car, architectural panels, energy
absorption purposes, or for the construction of interior or
exterior walls of a building. There is a demand for an all metal
composite panel construction, preferably a light-weight metal
panel, and which is easy to manufacture.
SUMMARY OF THE INVENTION
[0005] It is an object of the present invention to provide a
composite metal panel which is easy and reliable to
manufacture.
[0006] It is a further object of the present invention to provide a
composite metal panel which can be manufactured by means of
brazing.
[0007] It is a further object of the present invention to provide a
composite metal panel in which the parallel metal plates and/or
sheets may be dissimilar to each other and/or dissimilar to the
aluminium stiffener sheet.
[0008] It is a further object of the present invention to provide a
composite metal panel having aluminium stiffener sheet which may be
employed both as corrugated sheet and as a honeycomb-like
structure.
[0009] According to the invention in one aspect there is provided a
rigid composite metal panel including at least two metal parallel
plates and/or sheets secured to the peaks and troughs of a
corrugated aluminium stiffener sheet arranged between the parallel
plates and/or sheets, characterized in that the corrugated
aluminium stiffener sheet is an aluminium brazing sheet product
made from an aluminium brazing sheet product including a core sheet
(1) made of an aluminium alloy having on at least one surface of
the core sheet clad, and preferably on both sides, an aluminium
alloy clad layer (2), the aluminium alloy clad layer being made of
an aluminium alloy comprising silicon in an amount in the range of
2 to 18% by weight, preferably 5 to 14%, and a layer (3) including
nickel on the outer surface of said aluminium alloy clad layer.
[0010] According to the invention in another aspect there is
provided a rigid metal composite panel including at least two
parallel metal plates and/or sheets secured to aluminium stiffener
sheet having a honeycomb structure arranged between the parallel
plates and/or sheets, characterized in that the corrugated
aluminium stiffener sheet is made from an aluminium brazing sheet
product including a core sheet (1) made of an aluminium alloy
having on at least one surface of the core sheet clad, and
preferably on both sides, an aluminium alloy clad layer (2), the
aluminium alloy clad layer being made of an aluminium alloy
comprising silicon in an amount in the range of 2 to 18% by weight,
preferably 5 to 14%, and a layer (3) including nickel on the outer
surface of said aluminium alloy clad layer.
[0011] By the invention it is possible to provide a light-weight
all-metal composite metal panel which is very rigid, and may be
used for various load-bearing constructions. By the invention it is
possible to provide a composite metal panel which may be bonded or
secured together in a simple and reliable manner by means of a
brazing operation, in particular under controlled atmosphere
brazing ("CAB") conditions in the absence of a brazing flux
material, such as the commonly known NOCOLOK (trade name) brazing
flux material. It has been found that the aluminium brazing sheet
product used may be formed into corrugated sheet of various shape
by means of, e.g., roll-forming, and may also be formed into a
honeycomb-like shape. Suitable corrugated sheets have for example
the shape of flat peaks and troughs, a dovetail shape or curved
peaks and troughs. A suitable honeycomb-like structure may be
formed for example from two or more corrugate stiffener sheets each
with flat peaks and troughs and whereby the peak of one sheet is
brazed to the trough of the other corrugated sheet. The rigid
honeycomb-like structure will be formed in the same brazing
operation as in which the honeycomb-like structure is bonded by
means of brazing to the parallel metal plates or sheets.
Furthermore, the use of the present brazing sheet product for the
manufacture of composite metal panels allows for a honeycomb core
having various number of various density honeycomb portions, due to
variations in densities or other cell sizes.
[0012] In an embodiment of the composite metal panel according to
the invention the corrugated aluminium stiffener sheet is in the
form of turbulator sheet, and thereby allowing to design and to
manufacture particular rigid metal composite panels. Turbulator
sheet is an expression known in the art for manufacturing heat
exchangers.
[0013] In an embodiment of the composite metal panel according to
the invention the corrugated aluminium stiffener sheet is a formed
sheet having a plurality of cup-like cavities, which cup-like
cavities are aligned in essentially parallel rows and whereby in
alternating parallel rows the openings of the cup-like cavities are
facing opposed directions. The tip surfaces of the cup-like
cavities form the peaks or alternatively the troughs of the
corrugated stiffener sheet, and the tip surfaces are joined by
brazing to the parallel metal plates or sheets. The tip surfaces
may be flattened in order to increase the contact surface area with
the parallel metal plates or sheets, and thereby increasing the
strength of the joint after brazing. The cup-like cavities may have
several forms, such as circular, cylindrical, spherical or
cone-shaped. Corrugated stiffener sheet of this type allows for the
design and manufacture of composite metal panels with improved
stiffness in multiple directions. Corrugated stiffener sheets
having such a structure are known in the art per se and are in
particular applied as heat-shields in cars and trucks, in which
known application the sheet material is made from one aluminium
alloy only and is not made of brazing sheet, and in particular not
of brazing sheet comprising a core sheet having multiple metal
layers of different composition.
[0014] In an embodiment of the aluminium brazing sheet product said
layer comprising nickel further comprises bismuth in a range of at
most 5% by weight.
[0015] In accordance with the invention it has been found
surprisingly that the nickel layer does not need to comprise any
lead as a mandatory alloying addition in order to achieve good
brazeability. Surprisingly it has been found that equal or even
better results can be obtained if bismuth is added to the nickel
layer, such that the nickel layer can be kept essentially lead-free
and simultaneously also in the plating bath used for the deposition
of this Ni--Bi layer. This is of particular relevance since the use
of lead for manufacturing brazed components and used in various
market areas is undesirable and it is envisaged that in the near
future there might possibly even be a ban on lead comprising
products or products manufactured via one or more intermediate
processing steps comprising lead or lead-based components.
[0016] Preferably in this aluminium brazing sheet product the layer
comprising nickel or nickel-bismuth has a thickness of at most 2.0
.mu.m, preferably of at most 1.0 .mu.m, and more preferably of at
most 0.5 .mu.m. A coating thickness of greater than 2.0 .mu.m
requires a prolonged treatment time for plating, and may result in
wrinkling of the molten filler material during subsequent brazing.
A preferred minimum thickness for this Ni--Bi-containing layer is
about 0.25 .mu.m. Also other techniques such as thermal spraying,
Chemical Vapor Deposition ("CVD") and Physical Vapor Deposition
("PVD") or other known techniques for depositing of metals or metal
alloys from a gas or vapor phase may be used.
[0017] In an embodiment of the aluminium brazing sheet product the
aluminium clad layer is of an AA4000-series aluminium alloy
comprising Si in a range of 2 to 18% by weight, and preferably 5 to
14%, and further at least Mg in a range of at most 8% by weight,
and preferably at most 5%, and more preferably in a range of 0.05
to 2.5% by weight.
[0018] In an embodiment, the aluminium brazing sheet product
according to the invention is further characterized by a layer
comprising zinc or tin as a bonding layer between the outer surface
of the aluminium clad layer and the layer comprising nickel. By the
zinc or tin-comprising bonding layer a very effective bond between
the aluminium alloy clad layer and the layer comprising nickel is
formed, the bond remaining effective during subsequent deformation
of the aluminium brazing sheet, for example by roll forming to
obtain a corrugate stiffener sheet. The coverage of the nickel
layer is no longer dependent on the surface characteristics of the
bare clad layer. The aluminium brazing sheet product is suitable
for fluxless brazing under controlled atmosphere conditions. This
part of the invention is based in part on the insight that to
obtain a well-bonded nickel layer on the Si-containing aluminium
clad layer of the brazing sheet product, so that the bond remains
effective under large deformation, pre-treatment of the aluminium
clad layer is extremely important when manufacturing complex shapes
of corrugated sheet. The prior art processes apparently aimed at
applying the nickel in a distributed form, principally to the
silicon particles at the surface of the aluminium clad layer,
rather than trying to achieve a uniform nickel-lead layer. In the
present invention the surface of the Si-containing aluminium clad
alloy is altered in such way that the nickel coverage is
independent of the silicon particles at its surface. The nickel
plating does not take place on the silicon particles but on the
applied thin bonding layer comprising zinc or tin. Since the nickel
thus is deposited on the total surface of the aluminium alloy clad
layer the necessary reaction before brazing can take place much
more easily as compared to the process of the prior art. The zinc
or tin applied does not interfere at all during the brazing
process, and may contain a component to assist the brazing. Since
the nickel is deposited smoothly and uniformly on the surface, the
use of lead to promote wetting during brazing can be reduced or
avoided, or other elements such as bismuth may be used for this
purpose. A further important advantage of the nickel deposited
smoothly and uniformly on the surface is that the total amount of
nickel to be applied in order to achieve good fluxless brazing can
be reduced.
[0019] Preferably the applied thin bonding layer comprising zinc or
tin has a thickness of at most 0.5 .mu.m, more preferably at most
0.3 .mu.m (300 nm), and most preferably in the range of 0.01 to
0.15 .mu.m (10-150 nm). In the best results obtained a thickness of
about 30 nm has been used. A coating thickness of more than 0.5
.mu.m requires a prolonged treatment time, e.g. for displacement
plating, and is thought to have no further advantages for improving
the adhesion.
[0020] In an embodiment the aluminium brazing sheet is
characterized in that the bonding layer comprising zinc or tin is
applied by a direct zinc plating treatment, or by a zincate
treatment or a stannate treatment. Very good results may be
obtained with an immersion zincate treatment or immersion stannate
treatment, often also referred to as displacement plating. A
further advantage is that this treatment lends itself to
application in a continuous process operation.
[0021] Zincate treatments are known per se in the art for applying
layers onto aluminium. Stannate treatments are known in the art for
depositing a layer on aluminium to facilitate soldering, to improve
electrical conductivity, and also to give a lubricated surface to
aluminium alloy pistons for internal combustion engines during the
running-in period.
[0022] The zinc or tin layer applied may be essentially a pure zinc
or tin layer or may be primarily zinc or tin (e.g. at least 50
weight %). Minor amounts of impurity elements or deliberately added
elements may be present, as discussed in more detail below.
Typically impurity elements are present at less than 10%, more
usually less than 5% by weight in the zinc or tin layer. The zinc
or tin layer may contain less than 1% of other elements.
[0023] In an embodiment of the aluminium brazing sheet product each
aluminium alloy clad layer has a thickness ranging from about 2 to
20% of the total thickness of the total brazing sheet product
thickness. Typical aluminium clad layer thickness is in the range
of 40 to 80 micron. The core sheet has a thickness typically in a
range of at most 5 mm, more preferably in the range of 0.1 to 2.5
mm.
[0024] The core sheet of the aluminium brazing sheet product is
preferably made of an aluminium alloy, such as those of the AA3000,
AA5000, and AA6000-series aluminium alloys.
[0025] In a further embodiment of the composite metal panels
according to the invention, the aluminium brazing sheet product
comprising a core sheet being made of an aluminium alloy having on
at least one surface of the core sheet clad with, and preferably on
both sides, an aluminium clad layer being made of an aluminium
alloy (typically an AA4000-series alloy) comprising silicon in an
amount in the range of 2 to 18% by weight, and preferably 5 to 14%,
a layer comprising nickel on the outer surface of the aluminium
alloy clad layer, and a separately deposited metal layer on one
side of the layer comprising nickel, and the separately deposited
metal layer comprising a metal such that taken together the
aluminium alloy clad layer and all layers of the aluminium brazing
sheet product exterior thereto form a metal filler having a
liquidus temperature in the range of 490 to 570.degree. C., and
preferably in the range of 510 to 550.degree. C.
[0026] With this aluminium brazing sheet product according to the
invention there is provided a brazing sheet product which may be
brazed at significantly lower temperatures as compared to
traditional brazing temperatures, typically in the range of 575 to
600.degree. C., while still achieving a very strong and reliable
bonding. This brazing sheet product may be applied in both vacuum
brazing and fluxless brazing under controlled atmosphere
conditions, but there is a preference for the application of
fluxless CAB conditions. Such a brazing sheet product may be
manufactured on an industrial scale without the laborious use of
thin metal foils or sheets, which are difficult to manufacture
themselves. With this aluminium brazing sheet product it is
possible the braze also more unusual metals to each other into a
composite metal panel, for example aluminium sheet made of
AA5000-series alloys having Mg in a range of at most 6.0 weight
percent may be used, such as, but not limited thereto, AA5052,
AA5056, AA5083 and AA5059.
[0027] In an embodiment, on at least one side of the core sheet the
layer comprising a metal such that taken together the aluminium
clad layer and all layers exterior thereto form a metal filler
having a reduced liquidus temperature, comprises copper or
copper-based alloy, and more preferably the layer comprises at
least 60% by weight copper. Suitable copper-based alloys may be for
example brass or bronze.
[0028] Preferably the applied layer comprising copper or
copper-based alloy has a thickness of at most 10 micron, more
preferably of at most 7 micron. In the best results a thickness of
about 4 micron has been used.
[0029] In particular copper has been found to significantly reduce
the liquidus temperature of the resultant metal filler. However,
further metal layers may be applied in addition thereto.
[0030] In an embodiment the aluminium brazing sheet is
characterized in that the layer comprising copper or copper-based
alloy is deposited by electroplating. However, other techniques
such as thermal spraying, plasma spraying, CVD, PVD or other known
techniques for depositing of metals or metal alloys from a gas or
vapor phase may be used.
[0031] In an embodiment the layer comprising copper or copper-based
alloy being deposited by plating copper or copper-alloy using an
aqueous alkaline copper-cyanide based plating bath.
[0032] In an embodiment the layer comprising copper or copper-based
alloy being deposited by plating copper or copper-alloy using an
aqueous copper-phosphate based plating bath. This aqueous plating
bath demonstrated to be operational in a wide pH range, and can be
used on industrial scale plating lines using a high current
density, which in turn allows for fairly high line speeds. It can
be composed using standard and readily available chemicals, and
copper can easily be replenished to the plating bath.
[0033] An embodiment of the aluminium brazing sheet product is
characterized in that taken together the aluminium clad layer and
all layers exterior thereto, have a composition comprising at
least, by weight percent:
[0034] Si in the range of 5 to 10%, preferably 7 to 10%,
[0035] Cu in the range of 12 to 25%, preferably 12 to 18%,
[0036] Bi in the range of at most 0.25%, preferably 0.02 to
0.25%,
[0037] Ni in the range of 0.05 to 4%, preferably 0.05 to 3.0%,
[0038] Zn in the range of at most 20%, preferably at most 10%, more
preferably at most 0.25%,
[0039] Sn in the range of at most 5%,
[0040] Mg in the range of at most 5%,
[0041] balance aluminium and impurities.
[0042] A typical impurity element may be iron, in particular
originating from the aluminium clad layer, and which may be
tolerated in an amount of at most 0.8%. Other alloying elements may
be present, and will typically, but not exclusively, originate from
the aluminium clad layer. In this embodiment a metal filler is
obtained which has a liquidus temperature in the range of 510 to
550.degree. C., and allows for the manufacturing of composite metal
panels at significant lower temperatures compared to traditional
industrial scale brazing temperatures for devices such as heat
exchangers, and thereby allowing for a more unconventional choice
of aluminium alloys, namely including those having low melting
point constituants, for the parallel plates or sheets for the
composite metal panel.
[0043] In an advantageous embodiment the aluminium brazing sheet is
characterized in that the layer comprising nickel is deposited by
electroplating both nickel and bismuth using an aqueous lead-free
bath comprising a nickel-ion concentration in a range of 10 to 100
g/l and a bismuth-ion concentration in the range of 0.01 to 10 g/l,
and more preferably by plating both nickel and bismuth using an
aqueous lead-free bath comprising a nickel-ion concentration in a
range of 20 to 70 g/l and a bismuth-ion concentration in the range
of 0.02 to 5 g/l.
[0044] In this aspect of the invention it has been found
surprisingly that the nickel layer does not need to comprise any
lead as a mandatory alloying addition in order to achieve good
brazeability. Surprisingly it has been found that equal or even
better results can be obtained if bismuth is added to the nickel
layer, such that the nickel layer can be kept essentially lead-free
and simultaneously also the plating bath used for the deposition of
this Ni--Bi layer. By using this aqueous lead-free plating bath the
need for the addition of lead has been overcome, which is a
significant achievement from an environmental point of view.
[0045] The nickel-ion concentration to the aqueous bath can be
added via the addition of nickel chloride, nickel fluoborate,
nickel sulfamate, nickel acetate or nickel sulphate. However, there
is a preference to use the addition of nickel sulphate
(NiSO.sub.4). At a too high level of nickel salt in the aqueous
bath there is the risk of the crystallization of the salt in the
solution, which might damage a continuous process. At too low
levels the resultant bath becomes uneconomical due to too long
plating times and low current density.
[0046] Bi-ion in the concentration set out above can be added in
various ways to the aqueous bath. In theory many bismuth compounds
could be used for this purpose. However, many bismuth compounds
have been tried out but only very few appear to provide reliable
and reproducible results. For example the addition of bismuth
acetate has been tried, but it has been found that this compound
did not dissolve in the plating bath used, whereas the addition of
lead acetate did not result in any problems with respect to having
this compound dissolved. For example also the combination of a bath
of nickel-ions and bismuth-ions and a tartrate at a pH in the range
of more than 8 resulted in the formation of an undesirable Ni
containing sludge. This Ni containing sludge did not dissolve upon
heating, indicating amongst others that Ni is unstable in the
presence of a tartrate in the mentioned pH range. In accordance
with the invention very good results have been obtained when
Bi-ions are being added via the addition of one or more of the
group consisting of bismuth carbonate (Bi.sub.2(CO.sub.3).sub.3),
bismuth oxide (Bi.sub.2O.sub.3), bismuth citrate
(BiC.sub.6H.sub.5O.sub.7) and bismuth chloride (BiCl.sub.3). By
using bismuth carbonate or bismuth oxide in the presence of nickel
a suitable plating bath has been obtained which is stable at a very
wide pH range. At too high levels of Bi-ion concentration in the
aqueous bath the resultant deposit has an undesired high
Bi-concentration. Preferably the Bi-concentration in the resultant
Ni--Bi layer on the brazing sheet product is not more than 5
percent by weight, and preferably not more than 3 percent by
weight. At too low levels the resultant bath becomes uneconomical
due to too long plating times and low current density.
[0047] Plating baths using the following salts have proved
particularly effective, in grams per liter:
[0048] Nickel sulphate in a range of 45 to 450 g/l, and preferably
90 to 315 g/l,
[0049] Chloride-ion concentration in a range of 1 to 50 g/l, and
preferably 1 to 30 g/l,
[0050] Sodium citrate in a range of 55 to 180 g/l, and preferably
110 to 150 g/l,
[0051] Sodium gluconate in range of 2 to 90 g/l, and preferably 5
to 55 g/l,
[0052] Ammonium sulphate in a range of at most 270 g/l,
[0053] Bismuth oxide in a range of 0.02 to 22 g/l, and preferably
0.05 to 11 g/l, or Bismuth carbonate in a range of 0.03 to 29 g/l,
and preferably 0.06 to 14 g/l.
[0054] The addition of an ion from the group consisting of chloride
and fluoride is required for inducing anode corrosion.
[0055] The plating bath used can operate in a wide pH range of 2.5
to 10, and preferably in the range of 4 to 8, without affecting the
properties of the bath and without dissolving the aluminium clad
layer.
[0056] In an embodiment, the composite metal panel is characterized
in that one or more of the parallel metal plates or sheets is made
from a metal selected from the group consisting of aluminium,
aluminium alloy, titanium, plated or coated titanium, bronze,
brass, stainless steel, plated or coated stainless steel,
low-carbon steel, plated or coated low-carbon steel, high-strength
steel, and plated or coated high-strength steel, nickel or
nickel-alloy. An example of a suitable plated stainless steel sheet
or plate is copper plated material. Suitable stainless steel grades
are those with 0.01 to 0.35 weight % carbon and 11 to 27% by weight
Cr, as defined by the international steel numbers, like Ferritic
grades, for example ASTM 409, 410S, 430; Martensitic grades, for
example ASTM 420; Duplex grades, for example ASTM 329, S31803;
Austenitic grades, for example ASTM 301, 304L, 321, 316L; heat and
creep resisting grades, for example ASTM 309S, 304H.
[0057] In accordance with the invention it has been found that the
aluminium brazing sheet product as set out above may be joined to
the parallel plates or sheets of various metals by means of
brazing, in particular in an inert atmosphere brazing (CAB) process
in the absence of a brazing-flux material. The parallel plate or
sheets may be formed from aluminium alloys, such as but not limited
to, from the AA3000-series alloys being frequently used in
conventional brazing operations, but also from for brazing more
unusually aluminium alloys from the AA5000-series having magnesium
as an essential alloying element in a range of at most 6 weight
percent, and also aluminium alloys from the AA6000-series. The
composite metal panel may also be formed in only one brazing cycle
from different metal combination, for example one parallel metal
sheet or plate is made from copper-plated stainless steel and the
other parallel metal sheet or plate is made from low-carbon steel
by using the aluminium brazing sheet product set out above.
[0058] In a further aspect of the invention there is provided a
method of manufacturing rigid composite metal panels as set out
above. The method of manufacturing the rigid composite metal panel,
includes the steps of:
[0059] (a) providing parts of at least two parallel metal plates
and/or sheets and a corrugated aluminium stiffener sheet which is
made from the aluminium brazing sheet product of the invention set
out above;
[0060] (b) assembling the parts into an assembly such that the
aluminium stiffener sheet is arranged between the parallel metal
plates and/or sheets;
[0061] (c) joining the assembly into a rigid composite metal panel
by heating the assembly under a vacuum or in an inert atmosphere in
the absence of a brazing-flux material at elevated temperature of
less than 600.degree. C. for a period long enough for melting and
spreading of the molten filler to form a joint between each of the
parallel metal plates and/or sheets and the corrugated aluminium
stiffener sheet;
[0062] (d) cooling of the joined composite metal panel.
[0063] In the method, fluxless CAB operation is preferred.
BRIEF DESCRIPTION OF THE DRAWINGS
[0064] The invention will now be illustrated by a non-limitative
example, and with reference to the drawings, wherein:
[0065] FIG. 1 is a schematic longitudinal section showing the
aluminium brazing sheet product used in the composite metal panel
according to the invention;
[0066] FIG. 2 is a schematic longitudinal section showing the
aluminium brazing sheet product used in the composite metal panel
according to the invention;
[0067] FIG. 3 is a schematic cross-section of a composite metal
panel according to the invention;
[0068] FIG. 4 is a schematic cut-out cross-section of a composite
metal panel shown in FIG. 3.
[0069] FIG. 5 is a schematic cross-section of a composite metal
panel according to the invention;
[0070] FIG. 6 is a schematic cross-section of a composite metal
panel according to the invention;
[0071] FIG. 7 is a schematic perspective view of a particular shape
of corrugated aluminium stiffener sheet in accordance with the
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0072] FIG. 1 shows schematically a brazing sheet product used in a
composite metal panel according to the invention. The brazing sheet
product includes an aluminium core sheet (1) on both sides clad
with an aluminium alloy clad layer (2), a layer (3) comprising
nickel or nickel-bismuth on the outer surface of the aluminium
alloy clad layer (2), and a thin bonding layer (4) comprising zinc
or tin between the layers (2) and (3). The composition and the
thickness of the various layers and their advantages have been set
out above.
[0073] FIG. 2 shows also schematically a brazing sheet product used
in a composite metal panel according to the invention. In this
embodiment the brazing sheet product of FIG. 1 has been used and
whereby on the layer (3) comprising nickel or nickel-bismuth a
further metal layer (5), preferably comprising copper, has been
deposited to reduce the liquidus temperature of the metal filler
formed by the clad layer 1 and all layers exterior thereto on its
one side of the aluminium core sheet. The further metal layer (5)
may be applied on top of the nickel layer (3) (as shown) or
underneath the nickel layer (3) (not shown). The compositions of
the various layers and their advantages have been set out
above.
[0074] FIG. 3 is a schematic cross-section of a composite metal
panel according to the invention comprising two parallel metal
plates or sheets (6,7) joined to each other by brazing of the peaks
and troughs of a corrugated aluminium stiffener sheet. The
corrugated aluminium sheet formed by the aluminium brazing sheet
product set out in FIGS. 1 or 2 is V-shaped.
[0075] FIG. 4 is a schematic cut-out cross-section of the composite
metal panel shown in FIG. 3, and wherein a parallel metal plate or
sheet (7) is shown which has been joined to the corrugated
aluminium stiffener sheet (8) with a fillet (9) formed after
heating to elevated temperature of an assembly of parallel metal
plates or sheets and aluminium stiffener sheet, and whereby during
heating a molten filler is formed by the aluminium alloy clad layer
(2) and all metal layers (3,4,5) exterior to the aluminium alloy
clad layer (2), as shown in FIGS. 1 and 2, to form a strong bond or
joint between the separate parts.
[0076] FIG. 5 is a similar structure as set out for FIG. 3, and
wherein the corrugated aluminium sheet (8) formed by the aluminium
brazing sheet product set out in FIGS. 1 or 2 has flat peaks and
troughs.
[0077] FIG. 6 is a schematic cross-section of a composite metal
panel according to the invention formed by three parallel metal
plates or sheets (6,7,10) joined to each other via the peaks and
troughs of corrugated aluminium stiffener sheets (8). The
corrugated aluminium sheet formed by the aluminium brazing sheet
product set out in FIGS. 1 or 2 is V-shaped. The two different
aluminium stiffener sheets are oriented perpendicular to each other
in order to improve on the stiffness of the resultant composite
metal panel in different directions. It will be immediately
apparent to the skilled person that any angle of orientation
between the different aluminium stiffener sheet may be chosen
depending upon the desired stiffness of the composite metal panel.
The same applies for the shape of the aluminium stiffener
sheet.
[0078] FIG. 7 is a schematic perspective view of a particular shape
of corrugated aluminium stiffener sheet in accordance with the
invention, whereby the stiffener sheet is a formed sheet having a
plurality of cup-like cavities (11,12), which cup-like cavities are
aligned in rows and whereby in alternating parallel rows the
openings of the cup-like cavities are facing opposed directions.
The tip surfaces of the cup-like cavities form the peaks or
alternatively the troughs of the corrugated stiffener sheet, and
the tip surfaces are joined by brazing to the parallel metal plates
or sheets. As shown in FIG. 7 the tip surfaces may be flattened in
order to increase the contact surface area with the parallel metal
plates or sheets, and thereby increase the strength of the joint
after brazing. Depending on the desired stiffness of the composite
metal panel, the cup-like cavities may have several forms, such as
circular, cylindrical, spherical or cone-shaped. Corrugated
stiffener sheet of this type allows for the design and manufacture
of composite metal panels with improved stiffness in multiple
directions. The distance between two cup-like cavities aligned in
the same row may dependent on the application of the composite
metal panel, and is typically in the range of 10 to 30 mm. The
depth of the cup-like cavities may also be dependent on the
application, and is typically in the range of at most 25 mm.
EXAMPLE
[0079] On a laboratory scale testing was carried out on industrial
scale manufactured aluminium brazing sheet manufactured from an
AA3003 core alloy clad on both sides with an AA4045-series clad
alloy, having a total thickness of 0.5 mm, the thickness of each
clad being 10.9% of the total thickness. The composition of these
alloys is given in Table 1.
[0080] The brazing sheet was treated by the following sequential
process steps:
[0081] cleaning by immersion for 180 seconds in ChemTec (trade
name) 30014 (a commercial alkaline (etch) degreaser), and
rinsing,
[0082] alkaline etching for 20 sec. in ChemTec (trade name) 30203
(a commercial available alkaline etch cleaner), and rinsing,
[0083] desmutting for 4 sec. in an acidic oxidising solution,
typically 25-50 vol. % nitric acid, comprising ChemTec (trade name)
11093 (a commercial available pickle activator) at ambient
temperature, followed by rinsing,
[0084] zincate immersion using ChemTec (trade name) 024202 for 12
sec. at room temperature resulting in a zinc layer of about 30
nanometer, followed by rinsing,
[0085] nickel electroplating, and rinsing. The nickel comprising
layer has been applied using a nickel plating bath having a
composition as set out in Table 2 and having a pH of 5.5. The
Bi-ion concentration has been added to the plating bath using a
Bi-ion concentrate of 160 g/l sodium hydroxide, 300 g/l sodium
gluconate and 111 g/l bismuth oxide. The bismuth oxide could have
been replaced also by bismuth carbonate. The electroplating of a
Ni-Bi layer was performed at 57.degree. C. using a current density
of 6 A/dm.sup.2 and a plating time of 25 sec. About 10 g/m.sup.2 of
nickel was deposited and about 0.5 g/m.sup.2 bismuth, being the sum
of the applied layers on both sides on the brazing sheet product.
The bismuth content of the deposited alloy layer may easily be
varied, e.g. by lowering the bismuth concentration in the plating
bath to give a lower Bi content.
[0086] The aluminium brazing sheet product has been tested for
adhesion using the Erichsen dome test (5 mm), and the T-bend test.
A value assessment is then given to the adhesion of poor, fair or
good. The adhesion of the resultant brazing sheet product has been
accessed as good, allowing the aluminium brazing sheet product to
be subjected to considerable deformation operations such as typical
roll forming operations to obtain the required corrugated stiffener
sheet.
[0087] Following the adhesion test the aluminium brazing sheet
product has been corrugated into a corrugated sheet having V-shaped
peaks and troughs, and the space between two peaks was about 20 mm,
and the height of the corrugated sheet was about 8.5 mm. The
corrugated sheet has been placed between two parallel sheets of
AA3003-series material and also between two parallel sheets of
copper-plated stainless steel of 304L grade. Each parallel sheet
had dimensions of about 20.times.20 cm and a thickness of about 1
mm. Some pressure was applied to the unbrazed assembly during
brazing by putting a load of about 1 kg on the upper parallel metal
sheet. The assemblies were put in a brazing furnace and heated
under flowing nitrogen, with heating from room temperature to
580.degree. C., dwell time at 580.degree. C. for 1 minute, cooling
from 580.degree. C. to room temperature.
[0088] Both resultant composite metal panels had an excellent
brazed bonding between the parallel sheets and the corrugated
aluminium brazing sheet product. Both metal panels were very rigid,
which may be further optimised by choosing the shape of the
corrugated aluminium stiffener sheet. This experiment demonstrates
that by means of a single brazing operation a rigid composite metal
panel may be formed using the aluminium brazing sheet product.
Furthermore, there is no need to apply an additional additive, such
as a commonly used brazing flux material, prior to the brazing
operation, and this avoids several laborious processing steps and
also avoids the required removal of excess brazing flux material
after the brazing operation, which can be difficult with complex
shaped aluminium stiffener sheet or composite metal panels having
large dimensions. In order to obtain an excellent brazeability
there is no need for the mandatory addition of lead to the
nickel-layer. Similar or even better results may be obtained using
the addition of Bi to the layer comprising nickel. Optionally the
bismuth may also be added to the aluminium clad layer.
1TABLE 1 Weight percent. AA 3003 AA 4045 Si 0.6 max. 9.0-11.0 Fe
0.7 max. 0.8 max. Cu 0.05-0.20 0.30 max. Mn 1.0-1.5 0.05 max. Mg --
0.05 max. Zn 0.10 max. 0.10 max. Ti -- 0.20 max. impurities each
0.05 each 0.05 total 0.15 total 0.15 balance aluminium
aluminium
[0089]
2 TABLE 2 Compound Concentration [g/l] Nickel sulphate 142 Ammonium
sulphate 34 Nickel chloride 30 Sodium citrate 140 Sodium gluconate
30 Bismuth ions 1
[0090] 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. The present invention
is defined by the claims appended hereto.
* * * * *