U.S. patent application number 14/171209 was filed with the patent office on 2014-05-29 for aluminum alloy clad member adopted to heat exchanger, and core material for the same.
This patent application is currently assigned to Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.). The applicant listed for this patent is Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.). Invention is credited to Takahiro OZAWA, Shinji SAKASHITA, Satoshi YOSHIDA.
Application Number | 20140144613 14/171209 |
Document ID | / |
Family ID | 44352758 |
Filed Date | 2014-05-29 |
United States Patent
Application |
20140144613 |
Kind Code |
A1 |
SAKASHITA; Shinji ; et
al. |
May 29, 2014 |
ALUMINUM ALLOY CLAD MEMBER ADOPTED TO HEAT EXCHANGER, AND CORE
MATERIAL FOR THE SAME
Abstract
A core material for an aluminum alloy clad material contains Si
in a content of 0.3% to 1.5% (hereinafter "%" means "percent by
mass"), Mn in a content of 0.3% t 2.0%, Cu in a content of 0.3% to
1.5%, Ti in a content of 0.01% to 0.5%, and B in a content of
0.001% to 0.1%, with the remainder including Al and inevitable
impurities. The core material and an aluminum alloy clad material
using the same ensure sufficient corrosion resistance and give a
product having an extended life.
Inventors: |
SAKASHITA; Shinji;
(Kobe-shi, JP) ; OZAWA; Takahiro; (Kobe-shi,
JP) ; YOSHIDA; Satoshi; (Kobe-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.) |
Kobe-shi |
|
JP |
|
|
Assignee: |
Kabushiki Kaisha Kobe Seiko Sho
(Kobe Steel, Ltd.)
Kobe-shi
JP
|
Family ID: |
44352758 |
Appl. No.: |
14/171209 |
Filed: |
February 3, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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12984079 |
Jan 4, 2011 |
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14171209 |
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Current U.S.
Class: |
165/185 ;
428/646; 428/650; 428/654 |
Current CPC
Class: |
C22F 1/043 20130101;
C22C 21/00 20130101; C22F 1/04 20130101; C22F 1/057 20130101; B32B
15/016 20130101; F28F 21/084 20130101; C22C 21/02 20130101; F28F
21/089 20130101; C22C 21/14 20130101; Y10T 428/31678 20150401; C22C
21/12 20130101; C22C 21/16 20130101; Y10T 428/12764 20150115; Y10T
428/12708 20150115; Y10T 428/12736 20150115; B23K 1/0012 20130101;
F28F 19/06 20130101; B23K 35/286 20130101; B32B 15/017 20130101;
Y10S 165/905 20130101; C22C 21/04 20130101 |
Class at
Publication: |
165/185 ;
428/646; 428/650; 428/654 |
International
Class: |
F28F 21/08 20060101
F28F021/08 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 8, 2010 |
JP |
2010-025634 |
Claims
1-7. (canceled)
8. An aluminum alloy clad material comprising: a layer of the core
material; and a filler material layer clad on one or both sides of
the core material layer, wherein the filler material contains an
Al--Si alloy, a Zn alloy, or a Sn alloy, and wherein the core
material consists of: silicon (Si) in a content of 0.3 to 1.5
percent by mass, manganese (Mn) in a content of 0.3 to 2.0 percent
by mass, copper (Cu) in a content of 0.3 to 1.5 percent by mass,
titanium (Ti) in a content of 0.01 to 0.5 percent by mass, and
boron (B) in a content of 0.001 to 0.1 percent by mass, and at
least one element selected from the group consisting of: nickel
(Ni) in a content of 0.5 percent by mass or less (excluding 0%),
chromium (Cr) in a content of 0.5 percent by mass or less
(excluding 0%), niobium (Nb) in a content of 0.5 percent by mass or
less (excluding 0%), vanadium (V) in a content of 0.5 percent by
mass or less (excluding 0%), and zirconium (Zr) in a content of 0.5
percent by mass or less (excluding 0%), with the remainder
including aluminum (Al) and inevitable impurities.
9. An automobile heat exchanger comprising the aluminum alloy clad
material according to claim 8.
10. An automobile brazed radiator tube comprising the aluminum
alloy clad material as clamed in claim 8.
11. An aluminum alloy clad material comprising: a layer of the core
material; and a filler material layer clad on one or both sides of
the core material layer, wherein the filler material contains an
Al--Si alloy, a Zn alloy, or a Sn alloy, and wherein the core
material consists of: silicon (Si) in a content of 0.3 to 1.5
percent by mass, manganese (Mn) in a content of 0.3 to 2.0 percent
by mass, copper (Cu) in a content of 0.3 to 1.5 percent by mass,
titanium (Ti) in a content of 0.01 to 0.5 percent by mass, and
boron (B) in a content of 0.001 to 0.1 percent by mass, with the
remainder including aluminum (Al) and inevitable impurities.
12. An automobile heat exchanger comprising the aluminum alloy clad
material according to claim 11.
13. An automobile brazed radiator tube comprising the aluminum
alloy clad material as clamed in claim 11.
14. An aluminum alloy clad material comprising: a layer of the core
material; a filler material layer clad on one side of the core
material layer; and a sacrificial material layer clad on the other
side of the core material layer, wherein the filler material
contains an Al--Si alloy, a Zn alloy, or a Sn alloy, and wherein
the sacrificial material contains an Al--Zn alloy, and wherein the
core material consists of: silicon (Si) in a content of 0.3 to 1.5
percent by mass, manganese (Mn) in a content of 0.3 to 2.0 percent
by mass, copper (Cu) in a content of 0.3 to 1.5 percent by mass,
titanium (Ti) in a content of 0.01 to 0.5 percent by mass, and
boron (B) in a content of 0.001 to 0.1 percent by mass, with the
remainder including aluminum (Al) and inevitable impurities.
15. An automobile heat exchanger comprising the aluminum alloy clad
material according to claim 14.
16. An automobile brazed radiator tube comprising the aluminum
alloy clad material as clamed in claim 14.
17. An aluminum alloy clad material comprising a layer of the core
material; a filler material layer clad on one side of the core
material layer; and a sacrificial material layer clad on the other
side of the core material layer, wherein the filler material
contains an Al--Si alloy, a Zn alloy, or a Sn alloy, and wherein
the sacrificial material contains an Al--Zn alloy, and wherein the
core material consists of: silicon (Si) in a content of 0.3 to 1.5
percent by mass, manganese (Mn) in a content of 0.3 to 2.0 percent
by mass, copper (Cu) in a content of 0.3 to 1.5 percent by mass,
titanium (Ti) in a content of 0.01 to 0.5 percent by mass, boron
(B) in a content of 0.001 to 0.1 percent by mass, and at least one
element selected from the group consisting of: nickel (Ni) in a
content of 0.5 percent by mass or less (excluding 0%), chromium
(Cr) in a content of 0.5 percent by mass or less (excluding 0%),
niobium (Nb) in a content of 0.5 percent by mass or less (excluding
0%), vanadium (V) in a content of 0.5 percent by mass or less
(excluding 0%), and zirconium (Zr) in a content of 0.5 percent by
mass or less (excluding 0%), with the remainder including aluminum
(Al) and inevitable impurities.
18. An automobile heat exchanger comprising the aluminum alloy clad
material according to claim 17.
19. An automobile brazed radiator tube comprising the aluminum
alloy clad material as clamed in claim 17.
Description
TECHNICAL FIELD
[0001] The present invention relates to an aluminum alloy clad
material which is highly resistant to corrosion and is adopted to a
heat exchanger.
BACKGROUND ART
[0002] Heat exchangers such as radiators, condensers, and
evaporators to be mounted in automobiles are generally manufactured
by forming, assembling, and brazing aluminum alloy sheets, which
are lightweight and excel in heat conductivity. Most of aluminum
alloy core materials for use in such heat exchangers adopt Al--Mn
alloys having relatively high strengths. In addition, recently
developed core materials further contain alloy elements such as Cu,
Si, and Mg so as to have further higher strengths.
[0003] When such an aluminum alloy material for heat exchangers is
used as a tube typically in a radiator, the outer surface of the
tube is exposed to the atmosphere (air), and the inner surface is
exposed to a coolant such as cooling water. The tube, when exposed
to such a corrosive environment, may suffer from corrosion (pitting
corrosion) proceeding locally, resulting in the generation of
through holes (penetrating holes). For preventing corrosion of the
outer surface of the tube, so-called "sacrificial protection" is
generally employed and effective, in which a f in material
typically containing an Al--Zn alloy or another substance having a
less-noble potential than that of the aluminum alloy constituting
the tube is brought in contact with the tube. Also for preventing
corrosion of the inner surface of the tube, the sacrificial
protection technique is often employed. Specifically, in this case,
the tube is generally formed from a clad material including an
aluminum alloy core material, and clad on the inner side of the
core material, a sacrificial anode material (hereinafter also
referred to as a "sacrificial material") of an A--Zn alloy having a
less-noble potential than that of the aluminum alloy of the core
material. The outer surface of the tube is often clad with an
Al--Si alloy or another brazing material having a low melting
point, for the purpose of brazing typically with the fin
material.
[0004] As is described above, clad materials including three or
more layers and having a core material (core layer), and clad
thereon, a sacrificial material (sacrificial layer) and a brazing
material (brazing layer) are often used as aluminum alloy materials
for heat exchangers.
[0005] Increasing demands have been made on such aluminum alloys
for heat exchangers to have longer lives and smaller thicknesses
(lighter weights) and to have further higher corrosion resistance.
Exemplary techniques for further improving the corrosion resistance
of aluminum alloys for heat exchangers include those disclosed in
Japanese Unexamined Patent Application Publication (JP-A) No.
2009-228010 and Japanese Unexamined Patent Application Publication
(JP-A) No. 2008-231555. JP-A No. 2009-228010 discloses an aluminum
alloy brazing sheet in which compositions of the core material and
cladding are controlled. JP-A No. 2008-231555 discloses an aluminum
alloy composite material in which the composition of the core
material is controlled, and the distribution of Al--Mn
intermetallic compounds is also controlled.
SUMMARY OF INVENTION
Technical Problem
[0006] Although the outer surface of a heat exchanger can
relatively easily have corrosion resistance due to the sacrificial
protection effect of the fin material, the inner surface thereof
often suffers from the generation of through holes caused by
pitting corrosion and shows insufficient corrosion resistance,
unless a sacrificial layer having a sacrificial protection effect
is clad. The techniques disclosed in above-mentioned JP-A No.
2009-228010 and JP-A No. 2008-231555 ensure corrosion resistance to
some extent by the action of the cladding or the intermetallic
compounds. However, if the cladding or the intermetallic compounds
are corroded or damaged, the core material is exposed, and the
exposed core material can be corroded thereafter. Under such
circumstances, the present inventors came to consider that the core
material itself should have higher corrosion resistance in order to
allow the heat exchanger to have a further extended life.
[0007] Accordingly, an object of the present invention is to
provide a core material for an aluminum alloy clad material, and an
aluminum alloy clad material using the core material, both of which
ensure sufficient corrosion resistance to allow a heat exchanger to
have a further extended life.
[0008] The present invention achieves the object and provides, in
an embodiment, a core material for an aluminum alloy clad material,
which core material contains Si in a content of 0.3 to 1.5 percent
by mass; Mn in a content of 0.3 to 2.0 percent by mass; Cu in a
content of 0.3 to 1.5 percent by mass; Ti in a content of 0.01 to
0.5 percent by mass; and B in a content of 0.001 to 0.1 percent by
mass, with the remainder including Al and inevitable impurities.
This core material excels in corrosion resistance.
[0009] The core material may further contain (a) Mg in a content of
1.0 percent by mass or less (excluding 0%) and/or Ca in a content
of 1.0 percent by mass or less (excluding 0%); and/or (b) at least
one element selected from the group consisting of Ni in a content
of 0.5 percent by mass or less (excluding 0%), Cr in a content of
0.5 percent by mass or less (excluding 0%), Nb in a content of 0.5
percent by mass or less (excluding 0%), V in a content of 0.5
percent by mass or less (excluding 0%), and Zr in a content of 0.5
percent by mass or less (excluding 0%).
[0010] The present invention also provides, in another embodiment,
an aluminum alloy clad material which includes a layer of the core
material; and a filler material layer clad on one or both sides of
the core material layer, in which the filler material contains an
Al--Si alloy, a Zn alloy, or a Sn alloy. The present invention
further provides, in still another embodiment, an aluminum alloy
clad material which includes a layer of the core material; a filler
material layer clad on one side of the core material layer; and a
sacrificial material layer clad on the other side of the core
material layer, in which the filler material contains an Al--Si
alloy, a Zn alloy, or a Sn alloy, and the sacrificial material
contains an Al--Zn alloy.
[0011] The present invention further provides an automobile brazed
radiator tube using the aluminum alloy clad material. In a
preferred embodiment, the aluminum alloy clad material is adopted
to an automobile heat exchanger.
Advantageous Effects of Invention
[0012] The core material for an aluminum alloy clad material
according to the present invention contains Cu and Ti in
combination with an appropriate amount of boron (B), thereby
exhibits excellent corrosion resistance, and allows the heat
exchanger to have a longer life. In addition, the core material for
an aluminum alloy clad material according to the present invention
can exhibit excellent corrosion resistance even when the resulting
clad material has no sacrificial layer, and, when used typically in
an automobile heat exchanger tube, allows the tube to have a
smaller thickness and thereby allows the heat exchanger to have
both a lighter weight and a longer life.
DESCRIPTION OF EMBODIMENTS
[0013] The present inventors have made intensive investigations on
aluminum alloy materials (aluminum alloy members) for heat
exchangers which ensure sufficient corrosion resistance and thereby
allow extended lives of the heat exchangers. Such aluminum alloy
members for heat exchangers have very small thicknesses of about
0.3 mm and should be protected from pitting caused by pitting
corrosion. In known corrosion protection techniques using a
sacrificial material, pitting corrosion is prevented by the
sacrificial protection of the sacrificial material composed of an
Al--Zn alloy, because the Al--Zn alloy has a less-noble potential
than that of the aluminum alloy constituting the core material.
Specifically, the known corrosion protection techniques prevent or
inhibit the generation of pitting corrosion by allowing the entire
material to have a less noble potential by the presence of the
sacrificial material having a less-noble potential, so as not to
exceed the pitting corrosion potential of the core material. The
pitting corrosion potential is a critical potential over which
pitting corrosion is generated.
[0014] In contrast to this, the present inventors have conceived
that the pitting corrosion can be prevented by allowing the core
material itself to have a higher pitting corrosion potential (to
have a more-noble potential), even when the sacrificial material
does not exhibit its sacrificial protection effect due to the
corrosion or damage of the sacrificial material or even when a
sacrificial material layer is not provided. For increasing the
pitting corrosion potential of the core material itself, it is very
effective to add Cu and Ti in combination in appropriate amounts.
It should be noted that the use of Cu alone may possibly impair the
corrosion resistance of the aluminum alloy, because Cu has an
adverse effect of significantly accelerating a cathodic reaction of
corrosion, although it has an effect of increasing the pitting
corrosion potential of the aluminum alloy. To solve the adverse
effect of Cu, the present inventors have found that the addition of
boron (B) in an appropriate amount in combination with Cu can
cancel the cathodic reaction acceleration effect of Cu, namely, can
increase the pitting corrosion potential without loss of the
corrosion resistance.
[0015] The core material for an aluminum alloy clad material
according to the present invention should have an optimized
composition so as to have satisfactory properties such as corrosion
resistance, as well as strength and brazing ability necessary as a
member such as a heat exchanger tube. The reasons for adding
component elements and amounts thereof for use in the core material
for an aluminum alloy clad material according to the present
invention will be described below. All percentages herein are by
mass, unless otherwise specified.
[0016] Si in a Content of 0.3% to 1.5%
[0017] Silicon (Si) element is effective to improve the strength of
the aluminum alloy. Especially when added in combination with
manganese (Mn), Si and Mn form a Si--Mn precipitate, and this
further effectively improves the strength of the aluminum alloy.
Si, if in a content of less than 0.3%, gives a less amount of
dissolved Si and thereby insufficiently effectively improves the
strength. In contrast, Si, if in a content of more than 1.5%,
lowers the melting point of the core material, and this causes
melting of the core material during brazing. For these reasons, the
Si content is specified to be from 0.3% to 1.5%. The lower limit of
the Si content is preferably 0.35%, more preferably 0.4%, and
furthermore preferably 0.55%. The upper limit of the Si content is
preferably 1.45%, more preferably 1.4%, and furthermore preferably
1.0%.
[0018] Mn in a Content of 0.3% to 2.0%
[0019] Manganese (Mn) element is effective to improve the strength
of the aluminum alloy, as with Si. For effectively exhibiting the
activity, the Mn content is specified to be 0.3% or more. In
contrast, Mn, if in an excessively large content, causes
precipitation of coarse precipitates to impair workability, thus
undesirable when the core material is processed typically into a
heat exchanger tube. Thus, the Mn content is specified to be 2.0%
or less. The lower limit of the Mn content is preferably 0.35%,
more preferably 0.40%, and furthermore preferably 0.7%. The upper
limit of the Mn content is preferably 1.9%, more preferably 1.8%,
and furthermore preferably 1.6%.
[0020] Cu in a Content of 0.3% to 1.5%
[0021] Copper (Cu) element allows the aluminum alloy to have a
higher pitting corrosion potential and thereby to be resistant to
pitting corrosion. In addition, Cu effectively allows the aluminum
alloy to have a higher strength and is thereby necessary for a
higher strength of the clad material. To effectively exhibit these
activities, the Cu content is specified to be 0.3% or more. In
contrast, an excessively large amount of Cu may lower the melting
point of the aluminum alloy to cause the core material to melt
during brazing, thus being undesirable. For this reason, the Cu
content is specified to be 1.5% or less. The lower limit of the Cu
content is preferably 0.35%, more preferably 0.40%, and furthermore
preferably 0.50%. The upper limit of the Cu content is preferably
1.45%, more preferably 1.4%, and furthermore preferably 1.0%.
[0022] Ti in a Content of 0.01% to 0.5%
[0023] Titanium (Ti) element allows the aluminum alloy to have a
higher pitting corrosion potential and thereby to be resistant to
pitting corrosion, as with Cu. To exhibit these activities
effectively, the Ti content is specified to be 0.01% or more. In
contrast, an excessively large amount of Ti has an adverse effect
of impairing workability, and to avoid this, the Ti content is
specified to be 0.5% or less. The lower limit of the Ti content is
preferably 0.02%, more preferably 0.03%, and furthermore preferably
0.10%. The upper limit of the Ti content is preferably 0.45%, more
preferably 0.4%, and furthermore preferably 0.35%.
[0024] B in a Content of 0.001% to 0.1%
[0025] Boron (B) element has an activity of canceling the cathodic
reaction accelerating activity of Cu and is essential for improving
the corrosion resistance of the core material according to the
present invention. The activity of boron is probably based on that
boron undergoes corrosion and dissolution to form a borate, and
this acts as an inhibitor to the cathodic reaction. To exhibit the
activities effectively, the B content is specified to be 0.001% or
more. In contrast, boron impairs castability (flowability) upon
production of the aluminum alloy, and the B content is therefore
specified to be 0.1% or less. The lower limit of the B content is
preferably 0.002%, more preferably 0.003%, and furthermore
preferably 0.01%. The upper limit of the B content is preferably
0.095%, more preferably 0.09%, and furthermore preferably
0.07%.
[0026] The core material for an aluminum alloy clad material
according to the present invention has the basic composition as
mentioned above, with the remainder including substantially
aluminum. However, it is naturally acceptable that the core
material contains inevitable impurities (such as Fe and Zn) brought
typically from raw materials, construction materials, and
manufacturing facilities. The core material for an aluminum alloy
clad material according to the present invention may further
contain one or more of the following elements according to
necessity.
[0027] Mg in a content of 1.0% or less (excluding 0%) and/or Ca in
a content of 1.0% or less (excluding 0%)
[0028] Magnesium (Mg) and calcium (Ca) elements are both effective
for improving the corrosion resistance, because these elements
dissolve and thereby exhibit a pH increasing activity. This
prevents the pH from decreasing due to a hydrolysis reaction in a
local anode where Al dissolves and thereby prevents the corrosion
reaction. Among them, Mg, when coexisting with Si, forms Mg.sub.2Si
and other compounds as precipitates to contribute to improvements
in strength. To exhibit these activities effectively, the Mg
content and Ca content are each preferably 0.01% or more. In
contrast, excessively large amounts of Mg and Ca may lower the
brazing ability in a brazing process a fluoride flux. For this
reason, the Mg content and Ca content are each preferably 1.0% or
less. The lower limits of the Mg content and Ca content are each
more preferably 0.02%, furthermore preferably 0.03%, and especially
preferably 0.1%. The upper limits of the Mg content and Ca content
are each more preferably 0.95%, furthermore preferably 0.9%, and
especially preferably 0.7%.
[0029] At least one element selected from the group consisting of
Ni in a content of 0.5 percent by mass or less (excluding 0%), Cr
in a content of 0.5 percent by mass or less (excluding 0%), Nb in a
content of 0.5 percent by mass or less (excluding 0%), V in a
content of 0.5 percent by mass or less (excluding 0%), and Zr in a
content of 0.5 percent by mass or less (excluding
[0030] Nickel (Ni), chromium (Cr), niobium (Nb), vanadium (V), and
zirconium (Zr) have activities of improving the corrosion
resistance by strengthening a passive film formed on the surface of
the aluminum alloy and thereby allowing the aluminum alloy to be
resistant to pitting corrosion. These activities are developed
because the respective elements are enriched as stable oxides in
the surface layer of the aluminum alloy. To exhibit these
activities effectively, the contents of these elements are each
preferably 0.01% or more. In contrast, these elements, if present
in excessively large amounts, may lower the workability, and the
contents of the respective elements are each preferably 0.5% or
less. The lower limits of the Ni, Cr, Nb, V, and Zr contents are
each more preferably 0.02%, and furthermore preferably 0.03%. The
upper limits of the Ni, Cr, Nb, V, and Zr contents are each more
preferably 0.45%, furthermore preferably 0.4%, and especially
preferably 0.3%.
[0031] Embodiments of the present invention further include (i) an
aluminum alloy clad material including a layer of the core material
and a filler material layer clad on one or both sides of the core
material layer, in which the filler material contains an Al--Si
alloy, a Zn alloy, or a Sn alloy; and (ii) an aluminum alloy clad
material including a layer of the core material, a filler material
layer clad on one side of the core material layer, and a
sacrificial material layer clad on the other side of the core
material layer, in which the filler material contains an Al--Si
alloy, a Zn alloy, or a Sn alloy, and the sacrificial material
contains an Al--Zn alloy.
[0032] Brazing Material
[0033] As used herein the term "Al--Si alloy" refers to an aluminum
alloy containing Si in a content of about 5% to about 15% and may
be an aluminum alloy further containing, for example, Fe, Cu,
and/or Zn each in a content of about 1% or less, in addition to Si.
Silicon (Si) has an activity of allowing the Al--Si alloy to have a
lower melting point and is thereby an essential composition for the
brazing material. For this reason, the Si content in the Al--Si
alloy is preferably 5% or more. The presence of Si in a content of
5% or more further ensures the brazing ability necessary for the
heat exchanger, because Si also has an activity of improving
flowability in addition to the activity of lowering the melting
point. In contrast, Si, if present in an excessively large amount,
may impair the workability and may impede the processing of the
aluminum alloy clad material typically into a shape of a heat
exchanger tube, thus being undesirable. For this reason, the Si
content in the Al--Si alloy of the brazing material is preferably
15% or less. The Si content in the brazing material is more
preferably from 8% to 12%. Exemplary Al--Si alloys having such
compositions include the 4045 alloy, 4343 alloy, and 4004 alloy
specified in Japanese Industrial Standards (JIS).
[0034] As used herein the term "Zn alloy" refers to a zinc (Zn)
alloy containing Zn in a content of 60% or more; and the term "Sn
alloy" refers to a tin (Sn) alloy containing Sn in a content of 60%
or more. Exemplary Zn alloys and Sn alloys include S--Zn95Al5 and
S--Sn85Zn15 alloys prescribed in JIS Z3281 (Solders for Aluminum
and Aluminum Alloys).
[0035] Sacrificial Material
[0036] As used herein the term "Al--Zn alloy" refers to an aluminum
alloy containing Zn in a content of about 1% to about 10% and may
be an aluminum alloy further containing Fe in a content of about 0%
to about 1% and/or Mg in a content of about 0% to about 0.1%, in
addition to Zn. Exemplary Al--Zn alloys include a JIS 7072
alloy.
[0037] The core material, brazing material, and sacrificial
material in the clad material according to the present invention
have been described above. The clad material according to the
present invention preferably further includes an intermediate layer
between the core material layer and the brazing material the core
material may react with the fluoride in the flux to thereby lower
the brazing ability. For solving this problem, it is effective to
provide an intermediate layer having smaller Mg and Ca contents
between the brazing material layer and the core material layer. The
intermediate layer effectively exhibits its advantageous effect
particularly when the core material contains Mg in a content of
0.5% to 1.0% and/or Ca in a content of 0.5% to 1.0%. In this case,
the intermediate layer preferably has a Mg content of less than
0.5% and a Ca content of less than 0.5%. The upper limits of the Mg
content and Ca content are each more preferably 0.4% or less, and
furthermore preferably 0.3% or less. The intermediate layer may
have a composition other than Mg and Ca as with the composition of
the core material.
[0038] The clad material according to the present invention is
preferably controlled in clad ratios (proportions of thicknesses of
respective layers) and/or the thicknesses of the respective layers,
so as to have satisfactory basic properties necessary as a heat
exchanger tube or another member, such as corrosion resistance,
strength, and brazing ability. For improving the brazing ability,
the clad material preferably has a clad ratio of the brazing
material layer (the ratio of the thickness of the brazing material
layer to the total thickness of the clad material) of 5% or more
and/or has a thickness of the brazing material layer of 20 .mu.m or
more. In contrast, an excessively thick brazing material layer is
undesirable from the viewpoint of strength, and the clad material
preferably has a clad ratio of the brazing material layer of 30% or
less and/or has a thickness of the brazing material layer of 50
.mu.m or less. When an intermediate layer is provided so as to
inhibit the dispersion of Mg, Ca, and other elements adversely
affecting the brazing ability, the clad material preferably has a
clad ratio of the intermediate layer of 10% or more and/or has a
thickness of the intermediate layer of 20 .mu.m or more. In
contrast, an excessively thick intermediate layer may cause
insufficient strength, and the clad material preferably has a clad
ratio of the intermediate layer of 50% or less and/or has a
thickness of the intermediate layer of 100 .mu.m or less.
[0039] Although not specifically limited, the aluminum alloy clad
material according to the present invention can be manufactured,
for example, by the following method. Initially, raw materials are
melted and cast to yield ingots so as to have predetermined
compositions for the core material and the brazing material
respectively; the ingots are subjected, where necessary, to facing
and homogenization treatment and thereby yield an ingot for the
core material and an ingot for the brazing material. The respective
ingots are hot-rolled to desired thicknesses or are mechanically
sliced to desired thicknesses and thereby yield a core member, and
a brazing member. When a sacrificial material layer and/or an
intermediate layer is provided, a sacrificial member and an
intermediate member are manufactured in the above manner.
[0040] Next, the brazing member is laid on one or both sides of the
core member. In this process, when the sacrificial material layer
is provided, the sacrificial member is laid on a side of the core
member opposite to the brazing member. Where necessary, the
intermediate member is laid between the core member and the brazing
member. The resulting laminate is subjected to a heat treatment
(reheating) and to compression bonding through hot rolling. The
work is further subjected to cold rolling, process annealing, and
another cold rolling. After the cold rolling, the work may be
subjected to final annealing. The method may include any other
process such as strain removing process between, before, and/or
after the respective processes, within ranges not adversely
affecting the processes.
EXAMPLES
[0041] The present invention will be illustrated in further detail
with reference to several working examples below. It should be
noted, however, that these examples are never intended to limit the
scope of the present invention; various alternations and
modifications may be made without departing from the scope and
spirit of the present invention and are all included within the
technical scope of the present invention.
[0042] Preparation of Specimens
[0043] Aluminum alloys for core materials having the chemical
compositions given in Tables 1 to 3 were subjected to melting,
ingot-making, and casting at a casting temperature of 700.degree.
C. through continuous casting to give ingots, and the ingots were
homogenized at 530.degree. C. for 6 hours or shorter, were
hot-rolled, and thereby yielded core members.
TABLE-US-00001 TABLE 1 Composition of core material (percent by
mass) *the remainder being Al and inevitable impurities No. Si Mn
Cu Ti B Mg Ca Ni Cr Nb V Zr Si 0.49 0.80 0.23 -- -- -- -- -- -- --
-- -- S2 0.50 0.80 0.52 0.004 -- -- -- -- -- -- -- -- S3 0.50 0.79
0.50 0.15 0.0004 -- -- -- -- -- -- -- S4 0.30 0.50 0.50 0.15 0.020
-- -- -- -- -- -- -- S5 0.88 0.30 0.50 0.15 0.020 -- -- -- -- -- --
-- S6 0.88 0.80 0.30 0.14 0.020 -- -- -- -- -- -- -- S7 0.89 0.80
0.50 0.01 0.020 -- -- -- -- -- -- -- S8 0.90 0.80 0.53 0.15 0.001
-- -- -- -- -- -- -- S9 1.50 1.95 0.32 0.40 0.030 -- -- -- -- -- --
-- S10 0.69 2.00 0.51 0.29 0.030 -- -- -- -- -- -- -- S11 0.69 1.95
1.50 0.29 0.030 -- -- -- -- -- -- -- S12 0.68 1.19 0.65 0.50 0.030
-- -- -- -- -- -- -- S13 0.70 1.20 0.65 0.30 0.10 -- -- -- -- -- --
-- S14 0.70 1.20 0.62 0.15 0.030 1.00 -- -- -- -- -- -- S15 0.70
1.20 0.61 0.15 0.030 -- 1.00 -- -- -- -- -- S16 0.70 1.20 0.62 0.15
0.030 0.20 0.20 -- -- -- -- --
TABLE-US-00002 TABLE 2 Composition of core material (percent by
mass) *the remainder being Al and inevitable impurities No. Si Mn
Cu Ti B Mg Ca Ni Cr Nb V Zr S17 0.65 1.20 0.94 0.25 0.051 -- --
0.15 -- -- -- -- S18 0.65 1.20 0.94 0.25 0.051 -- -- -- 0.15 -- --
-- S19 0.65 1.20 0.94 0.25 0.051 -- -- -- -- 0.15 -- -- S20 0.65
1.20 0.94 0.25 0.051 -- -- 0.01 0.15 -- -- -- S21 0.65 1.20 0.94
0.25 0.051 -- -- -- 0.01 0.15 -- -- S22 0.65 1.20 0.94 0.25 0.051
-- -- -- 0.15 -- 0.05 -- S23 0.65 1.20 0.94 0.25 0.051 -- -- --
0.15 -- -- 0.05 S24 0.65 1.20 0.94 0.25 0.051 -- -- 0.06 0.05 0.50
-- -- S25 0.65 1.20 0.94 0.25 0.051 -- -- 0.06 0.05 -- 0.10 -- S26
0.65 1.20 0.94 0.25 0.051 -- -- 0.06 0.06 0.05 -- 0.05 S27 0.65
1.20 0.94 0.25 0.051 -- -- 0.05 0.06 0.05 0.06 -- S28 0.65 1.20
0.94 0.25 0.051 -- -- 0.05 0.05 0.05 0.05 0.05
TABLE-US-00003 TABLE 3 Composition of core material (percent by
mass) *the remainder being Al and inevitable impurities No. Si Mn
Cu Ti B Mg Ca Ni Cr Nb V Zr S29 0.60 1.50 0.61 0.20 0.030 0.60 --
-- 0.15 -- -- -- S30 0.60 1.50 0.61 0.20 0.030 -- 0.59 -- -- --
0.50 -- S31 0.60 1.50 0.61 0.20 0.030 0.01 0.60 -- -- -- -- 0.50
S32 0.60 1.50 0.61 0.20 0.030 0.60 -- 0.50 0.05 -- -- -- S33 0.60
1.50 0.61 0.20 0.030 0.60 -- 0.20 -- 0.01 -- -- S34 0.60 1.50 0.61
0.20 0.030 0.30 -- 0.10 -- -- 0.10 -- S35 0.60 1.50 0.61 0.20 0.030
-- 0.30 -- 0.10 0.10 -- -- S36 0.60 1.50 0.61 0.20 0.030 0.61 0.60
-- 0.10 -- -- 0.10 S37 0.60 1.50 0.61 0.20 0.030 0.61 -- 0.05 0.50
0.05 -- -- S38 0.60 1.50 0.61 0.20 0.030 0.61 -- 0.10 0.10 -- --
0.10 S39 0.60 1.50 0.61 0.20 0.030 0.60 -- -- 0.10 0.11 0.05 0.05
S40 0.60 1.50 0.61 0.20 0.030 -- 0.01 0.10 -- 0.11 0.05 0.05 S41
0.60 1.50 0.61 0.20 0.030 0.55 0.58 0.05 0.05 0.10 0.01 0.11 S42
0.60 1.50 0.61 0.20 0.030 0.20 0.20 0.10 0.10 0.05 0.05 0.01
[0044] As the brazing material, a brazing member was prepared by
melting and casting an Al-10% Si alloy corresponding to JIS 4045
standard to give an ingot, homogenizing the ingot at 500.degree. C.
for 3 hours, and hot-rolling the homogenized ingot.
[0045] The brazing member was laid on one side of the core member,
the resulting laminate was subjected to hot-rolling at 400.degree.
C. to 550.degree. C., then subjected to cold rolling, process
annealing, and another cold rolling, and thereby yielded clad
materials having a final gage of 0.25 mm. The structures or
configurations of the clad materials are as shown in Tables 4 to
6.
[0046] When a brazing technique is adopted to the manufacture of a
heat exchanger, added elements diffuse due to thermal diffusion
during heating for brazing. As a result, the resulting heat
exchanger suffers concentration gradients of the added elements.
For example, Si diffuses from the brazing material layer having a
relatively large Si content to the core material layer or
intermediate layer having a relatively small Si content. For
simulating the thermal diffusion of added elements upon heating for
brazing, the above-prepared clad materials were subjected to a
heating treatment at 600.degree. C. for 5 minutes, which conditions
corresponding to the brazing, and thereby yielded specimens for
corrosion test. Specifically, specimens for corrosion test 60 mm
long and 50 mm wide were cut from the aluminum alloy clad materials
after the heating treatment. The cut specimens were washed with
acetone, and, while defining a test surface as an area 50 mm long
and 40 mm wide of the core material layer surface, the surfaces of
the specimens other than the test surface, i.e., the outer
periphery 5 mm wide of the surface of the core material, the entire
side surfaces, and the entire surface of the brazing material layer
were covered with a silicone sealant.
[0047] Corrosion Test
[0048] To evaluate corrosion properties in an environment
simulating the inner surface of a radiator, the above-prepared
specimens were immersed in a solution simulating the cooling water,
and whether and how the specimens underwent corrosion were
determined. The solution used herein was an OY water containing 195
ppm by mass of Cl.sup.-, 60 ppm by mass of SO.sub.4.sup.2-, 1 ppm
by mass of Cu.sup.2+, and 30 ppm by mass of Fe.sup.3+ and having a
pH of 3.0. The solution in which each specimen was immersed was
subjected to temperature cycles for one month, each one cycle per
one day. In one cycle, the solution was heated from room
temperature to 88.degree. C. over 1 hour, held at 88.degree. C. for
7 hours, and cooled to room temperature over 1 hour, and held at
room temperature for 15 hours. In the corrosion test in this
experimental example, each five specimens were tested per each of
the aluminum alloy clad material samples in Tables 4 to 6, and
depth of local corrosion in the test surface (core material
surface) after the corrosion test was measured. The local corrosion
depths of the five specimens of each aluminum alloy clad material
sample were measured according to the focal depth method, and of
the measured five local corrosion depths, the deepest local
corrosion depth was defined as the maximum corrosion depth of the
sample in question. The specimens after the corrosion test were
immersed in nitric acid to remove corrosion products before the
measurements of the local corrosion depths. The results are shown
in Tables 4 to 6.
TABLE-US-00004 TABLE 4 Corrosion Core Brazing test material layer
material layer result Thick- Thick- Maximum ness ness corrosion
Overall No. Material (.mu.m) Material (.mu.m) depth (.mu.m)
judgement 1 S1 210 4045 40 penetrating Failure 2 S2 210 4045 40
penetrating Failure 3 S3 210 4045 40 penetrating Failure 4 S4 210
4045 40 103 Fair 5 S5 210 4045 40 105 Fair 6 S6 210 4045 40 102
Fair 7 S7 210 4045 40 103 Fair 8 S8 210 4045 40 101 Fair 9 S9 210
4045 40 104 Fair 10 S10 210 4045 40 102 Fair 11 S11 230 4045 20 105
Fair 12 S12 230 4045 20 102 Fair 13 S13 230 4045 20 100 Fair 14 S14
200 4045 50 82 Fair or Good 15 S15 200 4045 50 80 Fair or Good 16
S16 200 4045 50 79 Fair or Good
TABLE-US-00005 TABLE 5 Corrosion Core Brazing test material layer
material layer result Thick- Thick- Maximum ness ness corrosion
Overall No. Material (.mu.m) Material (.mu.m) depth (.mu.m)
judgement 17 S17 215 4045 35 65 Good 18 S18 215 4045 35 64 Good 19
S19 215 4045 35 68 Good 20 S20 215 4045 35 62 Good 21 S21 215 4045
35 62 Good 22 S22 215 4045 35 62 Good 23 S23 215 4045 35 64 Good 24
S24 215 4045 35 64 Good 25 S25 215 4045 35 64 Good 26 S26 215 4045
35 62 Good 27 S27 215 4045 35 62 Good 28 S28 215 4045 35 63
Good
TABLE-US-00006 TABLE 6 Core Brazing Corrosion material material
test layer layer result Thick- Thick- Maximum ness ness corrosion
Overall No. Material (.mu.m) Material (.mu.m) depth (.mu.m)
judgement 29 S29 205 4045 45 40 Excellent 30 S30 205 4045 45 39
Excellent 31 S31 205 4045 45 40 Excellent 32 S32 205 4045 45 39
Excellent 33 S33 205 4045 45 40 Excellent 34 S34 205 4045 45 41
Excellent 35 S35 205 4045 45 41 Excellent 36 S36 205 4045 45 41
Excellent 37 S37 205 4045 45 40 Excellent 38 S38 205 4045 45 35
Excellent 39 S39 205 4045 45 36 Excellent 40 S40 205 4045 45 37
Excellent 41 S41 205 4045 45 34 Excellent 42 S42 205 4045 45 36
Excellent
[0049] Samples Nos. 1, 2, and 3 were samples having a Cu content, a
Ti content, and a B content, respectively, in the core material of
less than the ranges specified in the present invention, thereby
showing insufficient corrosion resistance, and suffering from
penetration of pits through the clad materials caused by local
corrosion.
[0050] In contrast, Samples Nos. 4 to 42 had appropriately
controlled Cu, Ti, and B contents in the core material and showed
improved resistance to local corrosion. Among them, Samples Nos. 14
to 16 further contained Mg and/or Ca in addition to Cu, Ti, and B,
and Samples Nos. 17 to 28 further contained at least one element
selected from Ni, Cr, Nb, V, and Zr in addition to Cu, Ti, and B,
and these samples showed further improved resistance to local
corrosion. Samples Nos. 29 to 42 contained Mg and/or Ca in
combination with at least one element selected from Ni, Cr, Nb, V,
and Zr, in addition to Cu, Ti, and B, thereby showed very small
maximum corrosion depths of less than 50 .mu.m and exhibited very
excellent resistance to local corrosion.
* * * * *