U.S. patent application number 10/298539 was filed with the patent office on 2003-04-03 for multilayer metal composite products obtained by compound strand casting.
Invention is credited to Brandner, Dietmar Franz, Peter Haszler, Alfred Johann.
Application Number | 20030062143 10/298539 |
Document ID | / |
Family ID | 8224658 |
Filed Date | 2003-04-03 |
United States Patent
Application |
20030062143 |
Kind Code |
A1 |
Peter Haszler, Alfred Johann ;
et al. |
April 3, 2003 |
Multilayer metal composite products obtained by compound strand
casting
Abstract
A metallurgical product, such as brazing sheet, comprises a
core, on at least one side of the core an interlayer bonded to the
core and a cladding bonded to the interlayer. The core and the
interlayer are a compositely cast material having at their mutual
interface a bond formed in a casting process by their simultaneous
solidification from contacting melts of their respective materials.
This provides a simple process, with good adhesion. The cladding is
applied subsequently and the composite material is rolled into a
sheet or plate product.
Inventors: |
Peter Haszler, Alfred Johann;
(Vallendar, DE) ; Brandner, Dietmar Franz; (Mayen,
DE) |
Correspondence
Address: |
STEVENS, DAVIS, MILLER & MOSHER, LLP
Suite 850
1615 L Street N.W
Washington
DC
20036
US
|
Family ID: |
8224658 |
Appl. No.: |
10/298539 |
Filed: |
November 19, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10298539 |
Nov 19, 2002 |
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09319191 |
Aug 20, 1999 |
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6495269 |
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09319191 |
Aug 20, 1999 |
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PCT/EP97/06951 |
Dec 1, 1997 |
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Current U.S.
Class: |
164/76.1 ;
164/96; 428/612; 428/654 |
Current CPC
Class: |
Y10T 428/12472 20150115;
Y10T 428/12764 20150115; B22D 19/08 20130101; Y10T 428/12493
20150115; B32B 15/016 20130101; B22D 11/008 20130101; C22C 21/02
20130101; Y10T 428/12458 20150115; B23K 35/286 20130101; B22D
11/007 20130101 |
Class at
Publication: |
164/76.1 ;
428/654; 428/612; 164/96 |
International
Class: |
B32B 015/20; B22D
019/04 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 3, 1996 |
EP |
96203429.4 |
Claims
1. A metallurgical product comprising a core, on at least one side
of the core an interlayer bonded to the core and a cladding bonded
to the interlayer, characterized in that said core and interlayer
are a compositely cast material having at their mutual interface a
bond formed by their simultaneous solidification from contacting
melts of their respective materials in a casting process.
2. A metallurgical product comprising a core, on at least one side
of the core an interlayer bonded to the core and a cladding bonded
to the interlayer, characterized in that said core and interlayer
are a compositely cast material having at their mutual interface a
bonding zone formed by mutual mixing of their respective
compositions in the molten state prior to their solidification in a
casting process.
3. A metallurgical product according to claim 1 or 2, which is
plate or sheet and in which, on at least one side of said core,
said interlayer has, in the thickness direction of said plate or
sheet, a thickness in the range 1 to 30% of the thickness of said
compositely cast material.
4. A metallurgical product according to claim 1 or 2, which in
section transverse to the length direction of said bar, rod or
wire, said interlayer has a thickness which is in the range 1 to
30% of the radius of said compositely cast material.
5. A metallurgical product according to any one of claims 1 to 4,
wherein the core and the interlayer are essentially free from
oxides at their interface.
6. A metallurgical product according to any one of claims 1 to 5,
wherein the cladding has a solidus temperature different from that
of the core.
7. A metallurgical product according to claim 6, wherein the
cladding has a solidus temperature lower than that of the core.
8. A metallurgical product according to claim 6 or 7, wherein the
cladding is a brazing alloy.
9. A metallurgical product according to claim 8, wherein the
cladding is an aluminium brazing alloy.
10. A metallurgical product according to any one of claims 1 to 9,
wherein the core is an aluminium alloy.
11. A metallurgical product according to claim 10, wherein the core
comprises a heat treatable aluminium alloy.
12. A metallurgical product according to claim 11, wherein the core
comprises a non-heat treatable aluminium alloy.
13. A metallurgical product according to any one of claims 1 to 12,
wherein the interlayer has a corrosion potential different from
that of the core.
14. A metallurgical product according to any one of claims 1 to 13,
wherein the interlayer has a corrosion potential lower than that of
the core.
15. A metallurgical product according to any one of claims 1 to 14,
wherein the interlayer acts as a diffusion barrier between the
cladding and the core.
16. A metallurgical product according to any one of claims 13 to
15, wherein the interlayer comprises a heat treatable aluminium
alloy.
17. A metallurgical product according to any one of claims 13 to
15, wherein the interlayer comprises a non-heat treatable aluminium
alloy.
18. A metallurgical product in the form of sheet or plate,
comprising a compositely cast material comprising a core and an
interlayer bonded together by their simultaneous solidification,
and a cladding layer bonded to said interlayer after solidification
of the compositely cast material.
19. A method of producing a metallurgical product according to any
one of claims 1 to 18, comprising the steps of (i) preparing said
compositely cast material comprising said core and said interlayer
bonded to said core by a process including casting said core and
said interlayer in such a manner that their respective melts
solidify simultaneously and in contact with each other, and (ii)
bonding said cladding to said interlayer after solidification of
said interlayer.
20. A method according to claim 19, wherein, after casting, said
compositely cast material has a thickness of at least 100 mm.
21. A method according to claim 19 or 20, wherein said compositely
cast material is subjected to a homogenization heat treatment prior
to step (ii).
22. A method according to any one of claims 19 to 21, wherein said
compositely cast material is hot rolled prior to step (ii).
23. A method according to any one of claims 19 to 22, wherein said
compositely cast material is subjected to a surface treatment prior
to step (ii).
24. A method according to any one of claims 19 to 23, wherein after
step (ii), the product is rolled into a sheet or plate product.
25. A metallurgical product according to claim 1 in the form of a
sheet product for thickness less than 3 mm.
26. A metallurgical product according to claim 1 or 25, in the form
of brazing sheet.
27. A metallurgical product according to claim 26, wherein said
cladding in an aluminium alloy having a Si content in the range 3
to 18 weight %.
28. A metallurgical product according to claim 1 in the form of a
plate product having a thickness in the range 3 to 8 mm.
29. A brazed assembly comprising at least one component which is a
metallurgical product according to any one of claims 1 to 18.
Description
FIELD OF THE INVENTION
[0001] The invention relates to a metallurgical product comprising
a core, on at least one side of the core an interlayer bonded to
the core and a cladding bonded to the interlayer, and to a method
of producing such a metallurgical product. Particularly but not
exclusively, the invention relates to such a metallurgical product
in the form of a brazing sheet or a brazing plate, and also to a
brazed assembly including the metallurgical product as at least one
component.
DESCRIPTION OF THE PRIOR ART
[0002] A metallurgical product comprising a core alloy with on at
least one side an interlayer and at least one cladding layer, which
is bonded to the interlayer has been obtained by roll cladding the
different layers together. U.S. Pat. No. 2,821,014 typically
describes this method and product. A disadvantage of roll cladding
is the handling and processing, e.g. rolling and surface treatment,
of all the different types of layers. Consequently roll cladding is
time consuming and is expensive.
[0003] Direct adhesion of clad layers to a core layer to make
brazing sheet by rolling is also known, e.g. from EP-A-326337.
[0004] U.S. Pat. No. 5,476,725 describes a method of manufacture of
a composite brazing product having an aluminium core and at least
one clad layer. The clad layer or layers in band form are fed to
opposed cooled rolls simultaneously with molten core material,
which is solidified in contact with the clad layer or layers. It is
stated that, despite the fact that the clad layer melts at a lower
temperature than the core, it does not melt when it contacts the
molten core material in the roll bite. Subsequently the composite
is cold-rolled. In one variant of the method, interlayers of zinc
are thermally sprayed onto the clad bands as they are unwound from
coils prior to the contact of the bands with the molten core
material. A similar process is described in JP-A-56-091970.
[0005] JP-A-61-111745 describes a method of making a material
intended for brazing to another member to provide a corrosion and
wear resistant layer. Brazing metal is solidified as a band on one
roll of a pair of rolls, and a second molten metal in the form of a
Co alloy containing ceramic fibres is solidified onto the band at
the nip of the two rolls.
[0006] Some further prior art relating generally to casting
processes is discussed below.
SUMMARY OF THE INVENTION
[0007] An object of the invention is to provide a metallurgical
product of the type described above which can be produced at lower
costs compared to the existing products.
[0008] According to the invention in a first aspect there is
provided a metallurgical product comprising a core, on at least one
side of the core an interlayer bonded to the core and a cladding
bonded to the interlayer, characterized in that said core and
interlayer are a compositely cast material having at their mutual
interface a bond formed by their simultaneous solidification from
contacting melts of their respective materials in a casting
process.
[0009] According to the invention in a second aspect there is
provided a metallurgical product comprising a core, on at least one
side of the core an interlayer bonded to the core and a cladding
bonded to the interlayer, characterized in that said core and
interlayer are a compositely cast material having at their mutual
interface a bonding zone formed by mutual mixing of their
respective compositions in the molten state prior to their
solidification in a casting process.
[0010] The metallurgical product in accordance with this invention
is therefore characterized in that the core and the interlayer are
bonded in a casting process in which the core and the interlayer
are solidified simultaneously from the molten state as to form a
composite material. Subsequently, the clad layer is applied. The
core alloy and the interlayer alloy are simultaneously solidified
from the molten state during a continuous or semi-continuous
casting process in such a manner that the obtained solidified core
is covered at least on one side, and preferably on the whole outer
surface, with the interlayer alloy so as to form a compositely cast
material. Such a compositely cast material is obtained at
significant lower costs than a conventional roll clad composite
material, because scalping of the core alloy and the steps of
casting, rolling and surface treatment of the interlayer prior to
bonding onto the core are no longer required.
[0011] A further advantage of the invention is the excellent strong
bonding of the interlayer and the core, due to their simultaneous
solidification in contact with each other. This contact of the two
molten materials with consequent mixing at their interface produces
in the solidified product a narrow interface bonding zone which has
a metallurgical nature characteristic of the product and method of
this invention. Such an interface bonding zone is readily
recognizable by the expert in the product, and is different from
and distinguishable from the prior art products described above in
which one or both of two layers is solid prior to the bonding.
[0012] In the metallurgical product in accordance with the
invention, when in plate or sheet form, at least on one side of the
core the interlayer thickness is preferably 1-30% of the thickness
of the compositely cast material. In the case of a product of the
invention in the form of a bar, rod or wire, the interlayer is
likewise preferably 1-30% of the radius (half width) of the
compositely cast material. This allows for a great flexibility in
thickness of the interlayer, this flexibility being significantly
larger compared to roll cladding.
[0013] It is an advantage obtainable with the invention that the
core and the interlayer are essentially free from oxides at their
interface. An important advantage of such a compositely cast
material compared to roll bonded material is the improved bonding
between the core and the interlayer due to the absence of oxides or
oxide-compounds at their interface. Such compounds can be present
in roll bonded material even after proper surface treatment prior
to roll bonding.
[0014] In the metallurgical product in accordance with the
invention the cladding may have a solidus temperature different
from that of the core and more preferably the cladding has a
solidus temperature lower than that of the core. The metallurgical
product in these cases embodiments is very suitable for brazing
sheet applications.
[0015] While the invention is in principle applicable to a wide
range of metals, preferably the core is an aluminium alloy, which
makes the product suitable for a wide range of applications, e.g.
brazing sheet. Depending on the required final properties for the
application or use of the metallurgical product, one may select a
heat treatable aluminium alloy as the core alloy, e.g. AA2xxx,
AA6xxx or AA7xxx-series alloys, or a non-heat treatable aluminium
alloy, e.g. AA3xxx or AA5xxx-series alloys.
[0016] When the cladding is a brazing alloy, preferably it is an
aluminium brazing alloy. Depending on the final use or application
of the metallurgical product of the invention, also another
cladding can be applied, e.g. AA1xxx-series alloys to obtain a
mirror like surface finish, or the application of zinc or a zinc
alloy or a zinc containing aluminium alloy to improve corrosion
resistance.
[0017] Preferably the interlayer has a corrosion potential
different from that of the core, and more preferably lower than
that of the core. In this case the interlayer acts as an anodic
interlayer and improves the corrosion resistance of the
metallurgical product. Depending on the type of core alloy and the
application or use of the metallurgical product one may prefer an
interlayer comprising a heat treatable aluminium alloy, e.g.
AA2xxx, AA6xxx or AA7xxx-series alloys, or an interlayer comprising
non-heat treatable aluminium alloys, e.g. AA1xxx, AA3xxx or
AA5xxx-series alloys. Alternatively the use of zinc or a zinc alloy
or a zinc-containing aluminium alloy is possible.
[0018] Preferably the interlayer constitutes, in known manner, a
diffusion barrier between the cladding and the core. In this case
the interlayer shields the core material from elements coming from
the molten brazing alloy during brazing and vice versa. Depending
on the type of core alloy and the application or use of the
metallurgical product, one may prefer an interlayer AA6xxx or
AA7xxx-series alloys, or one may prefer an interlayer comprising a
non-heat treatable aluminium alloy, e.g. AA1xxx, AA3xxx or
AA5xxx-series alloys. See U.S. Pat. No. 2,821,014 for further
information concerning barrier liners for use in the present
invention.
[0019] Another object of this invention is to provide a method for
producing the metallurgical product of the invention.
[0020] The method in accordance with this invention comprises the
steps of
[0021] (i) preparing the compositely cast material comprising the
core and the interlayer bonded to the core by a process including
casting the core and the interlayer in such a manner that their
respective melts solidify simultaneously in contact with each
other, and
[0022] (ii) bonding the cladding to said interlayer after
solidification of said interlayer.
[0023] An advantage of this method is that the core and the
interlayer are bonded together in one process step, avoiding the
need for rolling a plate of the interlayer material and surface
treatments of the core and the interlayer material. In this way
significant process cost benefits are obtained. Another advantage
of the method according to the invention is the flexibility of
choice of the core alloy. Non-conventional core alloys can be
processed, e.g. high strength AA7xxx-series alloys having a
functional interlayer between the cladding and the core. the
core.
[0024] Any suitable casting process, particularly continuous and
semi-continuous casting processes can be used in the method of the
invention to form the compositely cast materials, e.g. the casting
techniques or processes known from the patent publications
EP-A-0596134 and DE-A-4420697. It is mentioned here for
completeness of prior art disclosure that many other combined
casting techniques in which two metals are solidified are known.
Examples are those of DE-A-844806, U.S. 4,567,936, GB-A-2204518 and
EP-A-596134, but these do not involve simultaneous solidification
of two molten metals in contact.
[0025] More preferably a DC-casting process or modification thereof
is used, e.g. that of DE-A-4420697, because in this way the method
can be applied at existing casting stations without the need for
significant cost investments for a new casting machine and required
infrastructures, both for ingots and extrusion billets.
[0026] In a preferred method of the invention the thickness of the
compositely cast material after casting is more than 100 mm, and in
the case of an extrusion billet the diameter of the composite
material is more than 100 mm, although smaller diameter billets can
be produced in the way ("extrusion billet" is a term used in the
art to describe typically a cylindrical product which may be
subjected to extrusion, though in the present invention a different
subsequent treatment such as rolling may be employed). This allows
for the production of the composite material using conventional
DC-casting techniques or small modifications thereof. Further cost
reductions are achieved in this way.
[0027] The bonding between the cladding and the interlayer can be
obtained using the conventional roll cladding technique or
modifications thereof. However, also other techniques like dipping,
thermal spraying or arc spraying the cladding onto the interlayer
may be used.
[0028] Background information on plating, coating, and surface
treatment may be found in the following two resources and in the
references cited in their bibliographies:
[0029] (1) Metals Handbook, 9th edition, Vol. 5, "Surface Cleaning,
Finishing and Coating", American Society for Metals (ASM), Metals
Park, Ohio (1982); and
[0030] (2) ASM Handbook, Vol. 18, "Friction, Lubrication and Wear
Technology", ASM International, Metals Park, Ohio (1992).
[0031] Among the various options of plating, coating and surface
treatment, roll cladding is preferred for plate and/or sheet
products of the present invention.
[0032] In the method of the invention it is preferred that the
compositely cast material is homogenized, and preferably
homogenized prior to step (ii). Depending on the type of alloy
chosen for the core and the interlayer, homogenization may be
required to enhance processing of the composite material for
instance to improve formability during rolling. Homogenization is a
known process step performed to reduce residual stresses from
casting and reduce micro-segregation of alloying elements.
[0033] Preferably the compositely cast material is hot rolled prior
to step (ii). Depending on the thickness required of the
compositely cast material it may be rolled, and more preferably hot
rolled, prior to the cladding. Preferably the compositely cast
material is homogenized prior to hot rolling.
[0034] The compositely cast material is typically surface treated
prior to step (ii). By surface treating, e.g. scalping, chemical
etching and many other possible treatments or combinations thereof,
the bonding between the interlayer and the cladding may be
improved.
[0035] The method may further include a step (iii) of rolling the
product into a sheet product or plate product. Heat treatments at
any stage during or after rolling may also be applied to obtain the
required final properties of the plate or sheet product or may be
applied to enhance processing during rolling.
[0036] The invention further relates to a sheet product obtained
from processing the metallurgical product according to the
invention or obtained from the method according to the invention,
wherein the sheet product has a thickness of less than 3 mm and
more preferably less than 2 mm. More in particular the invention
also relates to a sheet product obtained from processing the
metallurgical product according to the invention or obtained from
the method according to the invention, wherein the sheet product is
brazing sheet. Using the metallurgical product according to the
invention a wide variety of possible combinations of core,
interlayer and cladding can be obtained which are very suitable for
brazing sheet and brazing sheet applications. For example the
cladding comprises Si in a range of 3-18 weight %, or comprises an
aluminium alloy originating from the AA4xxx-series alloys.
[0037] Further the invention relates to a plate product obtained
from processing the metallurgical product according to the
invention or obtained from the method according to the invention,
wherein the plate product has a thickness in a range of 3-8 mm.
[0038] The invention also relates to the use of the metallurgical
product according to the invention or obtained from the method
according to the invention as brazing sheet, e.g. as part of an
assembly and bonding the assembly together. Or for use as part of
an assembly and bonding the assembly together by heating the
assembly above the solidus temperature of the cladding. Or as part
of an assembly comprising a heat exchanger of tube and fin or plate
and fin construction kept in heat exchanging relationship by
mechanical connection. Or for use as part of an assembly comprising
a heat exchanger of tube and fin or plate and fin construction kept
in yet another example for suitable use is as part of an assembly
comprising a heat exchanger or tube and fin or plate and fin
construction kept in heat exchanging relationship by the molten
cladding.
EXAMPLE
[0039] On a pilot scale in a test the following multilayer product
was produced.
[0040] A billet with a length of about 1500 mm and a total diameter
of 255 mm was cast using the casting technique of DE-A-4420697,
with simultaneous solidification of core and interlayer while their
respective melts are in contact. The diameter of the core was 221
mm and the remainder was the interlayer. The core alloy has a
chemical composition within the AA6063 range and the interlayer was
within AA3003 range with a further addition of 1.3 wt. % zinc. The
cast composite billet was cut lengthwise into sections of 500 mm.
The sections were homogenized for 8-12 hours at 560-580.degree. C.
with a heat-up and cooling rate of about 35.degree. C./hour. The
sections were hot-rolled into a rectangular shape of required
thickness. Alternatively forging might be applied. The interlayer
was scalped in order to obtain the required thickness of the layer
in the final thickness. The scalped section was roll clad with a
cladding on the interlayer on one side only. The cladding material
was within the AA4004 range. The multilayer product was hot rolled
down to 3.5 mm and further cold rolled to 0.35 mm. During cold
rolling an interanneal was applied at a temperature of 360.degree.
C. The final multilayer sheet product has a thickness of 0.35 mm of
which about 10% is the clad layer and 35-45 .mu.m is the
interlayer. The multilayer brazing sheet product was tested in a
SWAAT-test in accordance with ASTM G-85 and had a corrosion life of
more than 25 days without perforations. This is a similar test
result compared with multilayer brazing sheet obtained by
conventional roll cladding of similar composition and thickness of
the different layers.
[0041] In this manner a multilayer product is obtained that has the
following advantages:
[0042] has corrosion and mechanical properties similar to that of
conventional roll clad material;
[0043] has a great flexibility in alloy composition;
[0044] can be produced at existing production facilities;
[0045] is produced at lower cost;
[0046] has an improved bonding between the core and the interface
layer.
* * * * *