U.S. patent application number 16/091776 was filed with the patent office on 2019-05-30 for aluminum alloy fin material, aluminum alloy brazing sheet, and heat exchanger.
The applicant listed for this patent is UACJ Corporation. Invention is credited to Ryoko FUJIMURA, Tomohito KUROSAKI, Yoshihiko MIZUTA, Junji NINOMIYA.
Application Number | 20190162492 16/091776 |
Document ID | / |
Family ID | 60084541 |
Filed Date | 2019-05-30 |
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United States Patent
Application |
20190162492 |
Kind Code |
A1 |
KUROSAKI; Tomohito ; et
al. |
May 30, 2019 |
ALUMINUM ALLOY FIN MATERIAL, ALUMINUM ALLOY BRAZING SHEET, AND HEAT
EXCHANGER
Abstract
An aluminum alloy fin material includes an aluminum alloy
containing 1.50 to 5.00 mass % Si with the balance of Al and
inevitable impurities, and has the function of being bonded by
heating with a single layer. Assuming that in a cross section along
the thickness direction of the fin material, the equivalent circle
diameter of a Si particle is represented by D, a distance from a
surface layer to the center of the Si particle is represented by L,
the thickness of the fin material is represented by t, and a length
parallel to the surface layer is represented by W, all Si particles
that are present in the range of the length W and satisfy
D.gtoreq.L and L+D>0.04 t also satisfy
0.ltoreq..SIGMA..pi.D.sup.2<0.08 tW. An aluminum alloy brazing
sheet includes, as a skin material, the fin material that is clad
on a core material including an aluminum alloy. A heat exchanger
includes the fin material or the brazing sheet that is used in a
fin.
Inventors: |
KUROSAKI; Tomohito; (Tokyo,
JP) ; NINOMIYA; Junji; (Tokyo, JP) ; MIZUTA;
Yoshihiko; (Tokyo, JP) ; FUJIMURA; Ryoko;
(Tokyo, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
UACJ Corporation |
Tokyo |
|
JP |
|
|
Family ID: |
60084541 |
Appl. No.: |
16/091776 |
Filed: |
April 12, 2017 |
PCT Filed: |
April 12, 2017 |
PCT NO: |
PCT/JP2017/015001 |
371 Date: |
October 5, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F28F 1/022 20130101;
F28F 21/084 20130101; F28F 1/325 20130101; F28F 19/00 20130101;
B23K 35/288 20130101; B22D 21/007 20130101; B22D 11/003 20130101;
B23K 35/286 20130101; F28F 2215/12 20130101; B22D 11/22 20130101;
F28F 1/32 20130101; B22D 11/049 20130101; B23K 1/0012 20130101;
F28F 2275/04 20130101; C22C 21/00 20130101; C22F 1/043 20130101;
C22C 21/02 20130101; C22C 21/10 20130101; B23K 35/0233
20130101 |
International
Class: |
F28F 21/08 20060101
F28F021/08; F28F 19/00 20060101 F28F019/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 12, 2016 |
JP |
2016-079933 |
Mar 27, 2017 |
JP |
2017-060744 |
Claims
1. An aluminum alloy fin material comprising: an aluminum alloy
containing 1.50 to 5.00 mass % Si with a balance of Al and
inevitable impurities, wherein assuming that in a cross section
along a thickness direction of the fin material, an equivalent
circle diameter of a Si particle is represented by D, a distance
from a surface layer to a center of the Si particle is represented
by L, a thickness of the fin material is represented by t, and a
length parallel to the surface layer is represented by W, all Si
particles that are present in a range of the length W and satisfy
D.gtoreq.L and L+D>0.04 t also satisfy
0.ltoreq..SIGMA..pi.D.sub.2<0.08 tW.
2. The aluminum alloy fin material according to claim 1, wherein
the aluminum alloy further contains one or more selected from 0.01
to 2.00 mass % Fe, 0.05 to 2.00 mass % Mn, 0.05 to 6.00 mass % Zn,
and 0.05 to 1.50 mass % Cu.
3. An aluminum alloy brazing sheet comprising, as a skin material,
the fin material according to claim 1, wherein the fin material is
clad on a core material comprising an aluminum alloy.
4. A heat exchanger comprising the aluminum alloy fin material
according to claim 1, wherein the aluminum alloy fin material is
used in a fin.
5. A heat exchanger comprising the aluminum alloy brazing sheet
according to claim 3, wherein the aluminum alloy brazing sheet is
used in a fin.
6. An aluminum alloy brazing sheet comprising, as a skin material,
the fin material according to claim 2, wherein the fin material is
clad on a core material comprising an aluminum alloy.
7. A heat exchanger comprising the aluminum alloy fin material
according to claim 2, wherein the aluminum alloy fin material is
used in a fin.
8. A heat exchanger comprising the aluminum alloy brazing sheet
according to claim 6, wherein the aluminum alloy brazing sheet is
used in a fin.
Description
TECHNICAL FIELD
[0001] The present disclosure relates to an aluminum alloy fin
material, an aluminum alloy brazing sheet, and a heat
exchanger.
BACKGROUND ART
[0002] Conventionally, brazing fins of which the skin materials are
clad with Al--Si-based alloys have been commonly used as aluminum
alloy fin materials having the function of being bonded to tubes by
heating. In such a brazing fin, a skin material is melted and flows
in the case of heating and bonding, and therefore, a sheet
thickness is decreased according to the melting. Patent Literature
1 discloses a fin materials having the function of being bonded by
heating with a single-layer material but does not disclose
suppression of a decrease in sheet thickness.
[0003] For example, in each of the end edges of many sheet-shaped
fins arranged at a predetermined spacing from each other in a
fm-and-tube-type heat exchanger, plural notch grooves opened to
penetrate the same positions of the sheet-shaped fins are disposed
along each of the end edges. A structure is made in which collars
are formed on the notch grooves so as to come in contact with a
surface of a flat tube through which a heat-transfer fluid flows,
and in which the flat tube is fit in the notch grooves. The tube is
assembled, heated, and bonded in the state of extending in the
direction of overlapping such sheet-shaped fins, whereby the heat
exchanger is produced.
[0004] There is a problem that a clearance between a tube surface
and a fin surface becomes large when such a heat exchanger is
bonded and heated and the sheet thickness of a fin material is
reduced at the time of the bonding. There is a problem that when a
decrease in sheet thickness is large, it is impossible to fill the
clearance with a melted bonding assistant, and a bonding rate is
decreased.
[0005] A decrease in sheet thickness due to the heating for bonding
results in the deterioration of rigidity due to a decrease in the
cross-sectional area of the fin. There is a problem that,
therefore, it is necessary to use a fin material of which the
thickness is larger than a fin sheet thickness required after the
heating for bonding, resulting in an increase in the cost of the
material.
[0006] It is conceivable to use the fin material having the
function of being bonded by heating with a single layer "with a
very small dimensional change" disclosed in Patent Literature 1 in
order to suppress such a decrease in sheet thickness. However,
although it is described that a change in the dimension of the fin
material is very small, a decrease in sheet thickness is not
described in Examples, and deformation caused by bending stress
referred to as a sag test is merely described.
[0007] It is also conceivable to use, as a fin material, a brazing
fin having a decreased cladding ratio. However, a decrease in
cladding ratio in the fin material having a small sheet thickness
precludes production of the fin material.
CITATION LIST
Patent Literature
[0008] Patent Literature 1: Japanese Patent No. 5021097
SUMMARY OF INVENTION
Technical Problem
[0009] The present disclosure was accomplished with respect to the
above-described problems. An objective of the present disclosure is
to provide an aluminum alloy fin material, an aluminum alloy
brazing sheet, and a heat exchanger, which have a small decrease in
the sheet thickness of the fin material, the low deterioration of
bondability, and the low deterioration of rigidity in bonding and
heating.
Solution to Problem
[0010] In order to achieve the above-described objective, an
aluminum alloy fin material according to a first aspect of the
present disclosure is:
[0011] an aluminum alloy fin material including:
[0012] an aluminum alloy containing 1.50 to 5.00 mass % Si with the
balance of Al and inevitable impurities,
[0013] wherein assuming that in a cross section along the thickness
direction of the fin material, the equivalent circle diameter of a
Si particle is represented by D, a distance from a surface layer to
the center of the Si particle is represented by L, the thickness of
the fin material is represented by t, and a length parallel to the
surface layer is represented by W, all Si particles that are
present in the range of the length W and satisfy D.gtoreq.L and
L+D>0.04 t also satisfy 0.ltoreq..SIGMA..pi.D.sup.2<0.08
tW.
[0014] The aluminum alloy may further contain one or more selected
from 0.01 to 2.00 mass % Fe, 0.05 to 2.00 mass % Mn, 0.05 to 6.00
mass % Zn, and 0.05 to 1.50 mass % Cu.
[0015] An aluminum alloy brazing sheet according to a second aspect
of the present disclosure is:
[0016] an aluminum alloy brazing sheet including, as a skin
material, the aluminum alloy fin material, the aluminum alloy fin
material being clad on a core material including an aluminum
alloy.
[0017] A heat exchanger according to a third aspect of the present
disclosure is:
[0018] a heat exchanger including the aluminum alloy fin material,
the aluminum alloy fin material being used in a fin.
[0019] A heat exchanger according to a fourth aspect of the present
disclosure is:
[0020] a heat exchanger including the aluminum alloy brazing sheet,
the aluminum alloy brazing sheet being used in a fin.
Advantageous Effects of Invention
[0021] The aluminum alloy fin material, aluminum alloy brazing
sheet, and heat exchanger according to the present disclosure have
a small decrease in the sheet thickness of the fin material, the
low deterioration of bondability, and the low deterioration of
rigidity in bonding and heating. Specifically, since the rate of
decrease in sheet thickness after the heating is less than that
before the heating for bonding in the fin material, a clearance
generated between the fin material and another member at the time
of the heating for bonding can be suppressed. As a result, the fin
material having high bondability and the brazing sheet using the
fin material can be obtained. Since the less decrease in sheet
thickness can result in the less deterioration of rigidity after
the bonding, the thicknesses of the fin material and the brazing
sheet can be reduced, and the weight of the heat exchanger using
the fin material and the brazing sheet can be reduced.
BRIEF DESCRIPTION OF DRAWINGS
[0022] FIG. 1 is a perspective view of a heat exchanger according
to the present embodiment, which is used for evaluating
bondability, and in which plate-shaped fin materials and flat tubes
are combined; and
[0023] FIG. 2 is a front view of the sheet-shaped fin in FIG.
1.
DESCRIPTION OF EMBODIMENTS
[0024] As a result of intensive examination, the present inventors
found that the deterioration of the bondability and rigidity of a
fin material can be suppressed by controlling the rate of decrease
in sheet thickness after bonding the fin material to a tube with
respect to a sheet thickness before the bonding in order to solve
the problems. In addition, it was found that such suppression of
the rate of decrease in sheet thickness is achieved by
appropriately controlling particles included in a metal structure
in the vicinity of a surface layer.
[0025] An aluminum alloy fin material according to an embodiment of
the present disclosure will be described below.
[0026] 1. Metal Structure
[0027] 1-1. Regulation of Metal Structure
[0028] The aluminum alloy fin material according to the present
embodiment includes an aluminum alloy containing 1.50 to 5.00 mass
% Si with the balance of Al and inevitable impurities, and has the
function of being bonded by heating with a single layer. Assuming
that the thickness of the fin materials is represented by t, a
cross section along a thickness direction is considered, which is
divided into a cross section portion closer to one surface, from
one surface to the half of the thickness t, and a cross section
portion closer to the other surface, from the other surface to the
half of the thickness t.
[0029] Assuming that the equivalent circle diameter of a Si
particle is represented by D, a distance from the one or other
surface to the center of the Si particle is represented by L, and a
length parallel to a surface layer is represented by W, all Si
particles that are present in the range of the length W and satisfy
D.gtoreq.L and L+D>0.04 t also satisfy
0.ltoreq..SIGMA..pi.D.sup.2<0.08 tW. Here, .SIGMA..pi.D.sup.2 is
defined as the sum of cross-sectional areas .pi.D.sup.2 in the case
of melting all the Si particles that are present in the range of
the length W (the area of t.times.W) and satisfy D.gtoreq.L and
L+D>0.04 t in the whole of both the one and other cross section
portions (hereinafter referred to as "the whole cross
section").
[0030] For the units of D, L, t, and W, mm is applied.
[0031] 1-2. Mathematical Expressions Regulating Metal Structure
[0032] Mathematical expressions regulating the metal structure and
the numerical ranges of parameters will be described below.
[0033] (1) Si Particle Satisfying D.gtoreq.L
[0034] This mathematical expression indicates a condition for
allowing a melted Si particle to flow onto a surface when the Si
particle is melted. When being melted, the Si particle reacts with
a surrounding matrix and becomes a liquid phase having a spherical
shape of which the diameter is about 2 times the diameter of the Si
particle. The flow of the liquid phase onto the surface requires
that the radius of the liquid phase after the melting, that is, D,
which is 1/2 of the diameter 2D of the liquid phase, is not less
than the distance L from the surface to the center of the Si
particle. As described above, only Si particles satisfying
D.gtoreq.L flow onto the surface.
[0035] (2) Si Particle Satisfying L+D>0.04 t
[0036] This mathematical expression indicates a condition for
contributing to a decrease in sheet thickness by 8% or more when a
Si particle is melted and flows onto a surface. When a Si particle
having an equivalent circle diameter D at a distance L from a
surface is melted, a distance from the surface to the deepest
portion of a liquid phase is L+D. When the liquid phase flows onto
the surface, a sheet thickness of L+D is decreased in a site in
which the liquid phase has been present. A case in which a decrease
L+D in sheet thickness allowed to locally occur due to such one Si
particle is more than 4% of the thickness t of the whole cross
section in one or the other surface side causes a total decrease in
sheet thickness in both of the sides to be more than 8%. In
contrast, a case in which a decrease L+D in sheet thickness allowed
to locally occur due to one Si particle is 4% or less of the
thickness t of the whole cross section makes a limited contribution
to a decrease in sheet thickness. Accordingly, it is necessary to
control Si particles in which L+D is more than 4% of the thickness
t of the whole cross section in the one or other surface sides. In
other words, only the Si particles satisfying L+D>0.04 t are
regulated. In such a case, a decrease in sheet thickness in the one
or other surface side is preferably 3% or less, and is more
preferably controlled to 2% or less, with respect to the thickness
t of the whole cross section, for effectively preventing the
deterioration of bondability and rigidity.
[0037] (3) With Regard to Case in which Si Particles that are
Present in Range of Length W and Satisfy the (1) and (2) Described
Above in Whole Cross Section Also Satisfy
0.ltoreq..SIGMA..pi.D.sup.2<0.08 tW
[0038] Si particles that are present in the range of the length W
and satisfy the (1) and (2) described above in a cross section
portion closer to one surface flow onto the one surface and result
in a decrease in sheet thickness by more than 4% of the thickness t
of the whole cross section in the cross section portion closer to
the one surface when the Si particles are melted. Si particles that
are present in the range of the length W and satisfy the (1) and
(2) described above in a cross section portion closer to the other
surface flow onto the other surface and result in a decrease in
sheet thickness by more than 4% of the thickness t of the whole
cross section in the cross section portion closer to the other
surface when the Si particles are melted. Both of the Si particles
which result in the decreases in sheet thickness cause the sheet
thickness of the whole fin material to be decreased, and therefore,
bondability and rigidity are significantly deteriorated. However,
when the Si particles which satisfy the (1) and (2) described above
are locally present, the deterioration of the bondability and
rigidity is limited. Thus, the state of the presence of the Si
particles that are present in the range of the length W and satisfy
the (1) and (2) described above in the whole cross section of the
cross section portions closer to the one and other surfaces is
limited.
[0039] Specifically, the range of the area of the melted Si
particles satisfying the (1) and (2) described above in the whole
cross section, that is, .SIGMA..pi.D.sup.2 obtained by totalizing
.pi..times.(2D/2).sup.2=.pi.D.sup.2, is limited. When
.SIGMA..pi.D.sup.2 is low, a site in which a decrease in sheet
thickness occurs in the whole cross section is limited. With
increasing .SIGMA..pi.D.sup.2, a site in which a decrease in sheet
thickness occurs in the whole cross section is increased to
decrease the sheet thickness in the whole fin. In the present
embodiment, the rate of .SIGMA..pi.D.sup.2 to the area (t.times.W)
of the whole cross section described above is regulated to less
than 8%, that is, the area of .SIGMA..pi.D.sup.2 is regulated to
less than 0.08 tW. Here, in the case of .SIGMA..pi.D.sup.2=0, Si
particles which allow the sheet thickness to be decreased by 8% or
more in the whole cross section described above are not present,
and therefore, favorable bondability and favorable rigidity are
maintained. In the case of 0<.SIGMA..pi.D.sup.2<0.08 tW, a
decrease in sheet thickness occurs due to melting of Si particles,
but a region in which the decrease occurs is partial, and the
influence of the decrease on bondability and rigidity is limited.
In contrast, in the case of .SIGMA..pi.D.sup.2.gtoreq.0.08 tW, the
sheet thickness is decreased by 8% or more in the whole cross
section described above, that is, the rate of decrease in sheet
thickness in the whole fin material is 8% or more, the bondability
and rigidity of the fin material are significantly deteriorated.
The preferred range of .SIGMA..pi.D.sup.2 is
0.ltoreq..SIGMA..pi.D.sup.2<0.06 tW. Here, the rate (%) of
decrease in sheet thickness in the present embodiment is defined as
a value obtained by discarding digits to the right of the decimal
point of an actually determined numerical value.
[0040] Bondability is secured due to the presence of solid solution
Si or Si particles satisfying L+D.gtoreq.0.04 t even when
.SIGMA..pi.D.sup.2 is almost zero, and the amount of liquid phase
supplied from Si particles contributing to a decrease in sheet
thickness is small.
[0041] Each of the parameters described above will now be
described.
[0042] [Equivalent Circle Diameter D of Si Particle]
[0043] The equivalent circle diameter D of a Si particle is
typically about 0 to 10 .mu.M, and is up to about 30 .mu.m in a
case in which a coarse crystallized product is present. A case in
which a coarse crystallized product having an equivalent circle
diameter D of 30 .mu.m or more causes cracking, a pinhole, and/or
the like, and may preclude production. The case of 0 .mu.m means
that Si is completely solid-dissolved and is not present as Si
particles.
[0044] Here, the Si particle refers to: (1) pure Si; and (2) a Si
particle containing a slight amount of an element such as Ca or P
in part of pure Si. The equivalent circle diameter D of the Si
particle can be determined by observing a reflection electron image
of a cross section with a scanning electron microscope (SEM). It is
preferable to determine the equivalent circle diameter of the Si
particle by image analysis of an SEM photograph. The Si particle
and other particles are distinguished from each other on the basis
of the concentration difference of contrast by SEM-reflection
electron image observation. The element such as Ca or P contained
in the Si particle can be more precisely specified by an electron
probe micro analyzer (EPMA) or the like. Here, the cross section
refers to a cross section along the thickness direction of an
aluminum alloy material, and may be a cross section along an
optional direction such as a cross section along a rolling
direction or a cross section along a direction orthogonal to a
rolling direction as long as being along the thickness
direction.
[0045] [Distance L from Surface Layer of Fin Material to Center of
Si Particle]
[0046] The distance L from the surface layer of the fin material to
the center of the Si particle is not more than the sheet thickness
and is therefore less than the sheet thickness t. Here, L is
determined by measuring a distance from the center of the Si
particle to the surface layer of the fin material when the
above-described equivalent circle diameter of the Si particle is
determined. In such a case, the measurement can be performed by,
for example, taking a photograph of an SEM image of a visual field
from the surface layer of the fin material to the target Si
particle and performing the analysis of the image. When the Si
particle is not a uniaxial crystal, the intermediate position
between the point closest to the surface layer of the fin material
and the point farthest from the surface layer of the fin material
in the Si particle is regarded as the center of the Si
particle.
[0047] [Sheet Thickness t of Fin Material]
[0048] Typically, use of a fin material having a sheet thickness t
of about 0.01 to 0.2 mm is preferred from the viewpoint of weight
reduction and workability although t is not particularly limited. A
thin fin material of about 0.01 to 0.1 mm or a thick fin material
of more than 0.1 mm and about 0.2 mm is used. The sheet thickness t
of the fin material is preferably measured with a micrometer. In
such a case, in order to determine a difference before and after
bonding and heating, the difference is evaluated with the
arithmetic mean value of measurements of three or more sheet
thicknesses at the same position before and after the heating for
bonding for each sample.
[0049] 1-3. Principle of how Metal Structure Shows Effect
[0050] The fin material of the present embodiment exhibits a
bonding function with a single layer by melting a part of the
material to generate a liquid phase at the time of bonding and
heating. Si particles in the material react with a surrounding
matrix at the time of the bonding and heating, whereby a part of
the liquid phase is generated. In such a case, when coarse Si
particles are present in a surface layer, melting of the Si
particles results in a greater decrease in sheet thickness. Thus,
the present inventors found that a decrease in sheet thickness is
suppressed by controlling the sizes of Si particles in a surface
layer.
[0051] 2. Material
[0052] 2-1. Configuration
[0053] The fin material according to the present embodiment is
basically used as a fin material having the function of being
bonded by heating with a single layer. However, since the effect of
suppressing a decrease in the sheet thickness of a surface layer
can be similarly obtained even when a brazing fin is made by
cladding the fin material according to the present embodiment on
another material (core material), the fin material has an advantage
that it is not necessary to decrease a cladding ratio. As described
above, the fin material according to the present embodiment can
also be used in the form of a clad material (brazing fin).
[0054] The following description will be given based on the
presumption that the fin material according to the present
embodiment is used as a single-layered material. In the
above-described clad material in which the fin material according
to the present embodiment is used, however, the effect of
suppressing a decrease in sheet thickness in the portion of the fin
material according to the present embodiment can also be obtained
according to the following description.
[0055] 2-2. Alloy Composition
[0056] The aluminum alloy included in the fin material according to
the present embodiment contains 1.50 to 5.00 mass % (hereinafter
simply referred to as "%") Si as an essential element with the
balance of Al and inevitable impurities. In addition, the aluminum
alloy may further contain, as first selective additional elements,
one or more selected from 0.01 to 2.00% Fe, 0.05 to 2.00% Mn, 0.05
to 6.00% Zn, and 0.05 to 1.50% Cu.
[0057] 2-2-1. Si: 1.50 to 5.00%
[0058] Si is an element that generates an Al--Si-based liquid phase
and contributes to bonding. However, when the content of Si is less
than 1.50%, it is impossible to generate a sufficient amount of
liquid phase, the less bleeding of the liquid phase occurs, and the
bonding becomes incomplete. In contrast, when the content is more
than 5.00%, the amount of generated liquid phase portion in the
aluminum alloy material is increased, and therefore, the strength
of the aluminum alloy material which is being heated is decreased,
thereby precluding maintaining of the shape of a structure. In
addition, the number of Si particles present in the vicinity of the
surface layer is also increased, and therefore, the sheet thickness
is also significantly decreased. Accordingly, the content of Si is
regulated to 1.50 to 5.00%. The content of Si is preferably 1.50 to
3.50%, and more preferably 2.00 to 3.00%. Since the amount of
bleeding liquid phase portion is increased with increasing the
volume of the fin material and with increasing a heating
temperature, the amount of liquid phase portion required at the
time of the heating is adjusted according to the amount Si required
depending on the structure of the produced structure and according
to a heating temperature at the time of the bonding.
[0059] 2-2-2. Fe: 0.01 to 2.00%
[0060] Fe has the effect of being slightly solid-dissolved in a
matrix to improve strength and having the effect of being dispersed
as a crystallized product or precipitate to prevent strength from
decreasing particularly at high temperature. A case in which the
content of Fe is less than 0.01% not only prevents the
above-described effects from being sufficiently obtained but also
requires use of a high-purity base metal, thereby resulting in an
increase in material cost. In contrast, a case in which the content
of Fe is more than 2.00% results in, during casting, generation of
a coarse intermetallic compound, which therefore causes cracking
during working, thereby precluding the production of the fin
material. When a bonded body is exposed to a corrosive environment
(a corrosive environment in which a corrosive liquid particularly
flows), corrosion resistance is deteriorated. Further, crystal
grains recrystallized by the heating in the bonding are fragmented,
thereby increasing a grain boundary density, and therefore, the
amount of deformation during the bonding is increased, thereby
increasing a variation in the dimension of the fin material before
and after the bonding. Accordingly, the content of Fe is set to
0.01 to 2.00%. The content of Fe is preferably 0.20 to 1.00%.
[0061] 2-2-3. Mn: 0.05 to 2.00%
[0062] Mn is an additional element that acts as an element which
forms, together with Si and Fe, an Al--Mn--Si-based,
Al--Mn--Fe--Si-based, or Al--Mn--Fe-based intermetallic compound,
and is dispersed in an aluminum matrix to strengthen the fin
material, or that acts as an element which is solid-dissolved in an
aluminum matrix to strengthen the fin material, thereby improving
strength. When the content of Mn is more than 2.00%, a coarse
intermetallic compound is prone to be formed, and corrosion
resistance is deteriorated. In contrast, when the content of Mn is
less than 0.05%, the above-described effects become insufficient.
Accordingly, the content of Mn is set to 0.05 to 2.00%. The content
of Mn is preferably 0.10 to 1.50%.
[0063] 2-2-4. Zn: 0.05 to 6.00%
[0064] Zn is an element that is effective in the improvement of
corrosion resistance due to sacrificial protection action. Zn has
the action of being roughly uniformly solid-dissolved in a matrix
and allowing natural-potential to be lower. The sacrificial
protection action of relatively suppressing the corrosion of a
bonded tube can be exhibited by allowing the fin material according
to the present embodiment to be baser. When the content of Zn is
less than 0.05%, the effect of lower potential becomes
insufficient. In contrast, when the content of Zn is more than
6.00%, a corrosion rate is increased, self-corrosion resistance is
deteriorated, and sacrificial protection action is also
deteriorated. Accordingly, the content of Zn is set to 0.05 to
6.00%. The content of Zn is preferably 0.10 to 5.00%.
[0065] 2-2-5. Cu: 0.05 to 1.50%
[0066] Cu is an element that has the effect of being
solid-dissolved in a matrix and improving strength. When the
content of Cu is more than 1.50%, corrosion resistance is
deteriorated. In contrast, when the content of Cu is less than
0.05%, the above-described effects become insufficient.
Accordingly, the content of Cu is set to 0.05 to 1.50%. The content
of Cu is preferably 0.10 to 1.00%.
[0067] As selective additional elements, one or more selected from
0.05 to 2.00% of Mg, 0.05 to 0.30% of In, 0.05 to 0.30% of Sn, 0.05
to 0.30% of Ti, 0.05 to 0.30% of V, 0.05 to 0.30% of Cr, 2.00% or
less of Ni, and 0.30% or less of Zr may be further contained as
second selective additional elements, instead of or in addition to
the first selective additional element described above.
[0068] 2-2-6. Mg: 0.05 to 2.00%
[0069] Mg exhibits the action of age hardening due to Mg.sub.2Si
after bonding and heating, and strength is improved by the age
hardening. As described above, Mg is an additional element that
exhibits the effect of improvement in strength. When the content of
Mg is more than 2.00%, Mg reacts with a flux, whereby a compound
having a high melting point is formed, and therefore, bondability
is significantly deteriorated. In contrast, when the content of Mg
is less than 0.05%, the above-described effects become
insufficient. Accordingly, the content of Mg is set to 0.05 to
2.00%. The content of Mg is preferably 0.10 to 1.50%.
[0070] 2-2-7. In and Sn: 0.05 to 0.30%
[0071] Sn and In show the effect of exhibiting sacrificial
protection action. When the content of each of Sn and In is more
than 0.30%, a corrosion rate is increased, and self-corrosion
resistance is deteriorated. In contrast, when the content of each
of Sn and In is less than 0.05%, the above-described effects are
small. Accordingly, the content of each of Sn and In is set to 0.05
to 0.30%, and is preferably 0.10 to 0.25%.
[0072] 2-2-8. Ti and V: 0.05 to 0.30%
[0073] Ti and V exhibit the effects of not only being
solid-dissolved in a matrix to improve strength but also being
distributed in a layer form to prevent corrosion from proceeding in
a sheet thickness direction. When the content of each of Ti and V
is more than 0.30%, a coarse crystallized product is generated,
thereby inhibiting moldability and corrosion resistance. In
contrast, the content of each of Ti and V is less than 0.05%, the
effects are small. Accordingly, the content of each of Ti and V is
set to 0.05 to 0.30%, and is preferably 0.10 to 0.25%.
[0074] 2-2-9. Cr: 0.05 to 0.30%
[0075] Cr improves strength by solid solution strengthening and
allows crystal grains after heating to be coarsened by the
precipitation of an Al--Cr-based intermetallic compound. When the
content of Cr is more than 0.30%, a coarse intermetallic compound
is prone to be formed, and plastic workability is deteriorated. In
contrast, when the content is less than 0.05%, the above-described
effects are small. Accordingly, the content of Cr is set to 0.05 to
0.30% or less, and is preferably 0.10 to 0.25%.
[0076] 2-2-10. Ni: 2.00% or Less
[0077] Ni is crystallized or precipitated as an intermetallic
compound and exhibits the effect of improving strength after
bonding by dispersion strengthening. The content of Ni is set to
2.00% or less, and preferably 0.05 to 2.00%. When the content of Ni
is more than 2.00%, a coarse intermetallic compound is prone to be
formed, workability is deteriorated, and self-corrosion resistance
is deteriorated.
[0078] 2-2-11. Zr: 0.30% or Less
[0079] Zr is precipitated as an Al--Zr-based intermetallic compound
and exhibits the effect of improving strength after bonding by
dispersion strengthening. The Al--Zr-based intermetallic compound
coarsens crystal grains during heating. When the content of Zr is
more than 0.30%, a coarse intermetallic compound is prone to be
formed, and plastic workability is deteriorated. Accordingly, the
content of Zr is set to 0.30% or less. The content of Zr is
preferably 0.05 to 0.30%.
[0080] As a selective additional element, one or more selected from
0.1000% or less of Be, 0.1000% or less of Sr, 0.1000% or less of
Bi, 0.1000% or less of Na, and 0.0500% or less of Ca may be further
contained as a third selective additional element, instead of the
first selective additional element and second selective additional
element described above or in addition to either or both
thereof.
[0081] 2-2-12. Be, Sr, Bi, and Na: 0.1000% or Less, and Ca: 0.0500%
or Less
[0082] These elements exhibit the action of allowing bondability to
be further favorable by improving the characteristics of a liquid
phase by setting the elements in the ranges described above. In
other words, these trace elements can contribute to suppression of
a decrease in sheet thickness by fine dispersion of Si particles.
Bondability can be improved by improvement in the flowability of a
liquid phase, and/or the like. The preferred ranges of these
elements, Be, Sr, Bi, Na, and Ca, are 0.0001 to 0.1000%, 0.0001 to
0.1000%, 0.0001 to 0.1000%, 0.0001 to 0.1000%, and 0.0001 to
0.0500%, respectively. When these trace elements have contents of
less than the lower limit values regulated in the preferred ranges
described above, the effects such as the fine dispersion of Si
particles and improvement in the flowability of a liquid phase may
be insufficient. When these trace elements have contents of more
than the upper limit values regulated in the preferred ranges
described above, a harmful effect such as the deterioration of
corrosion resistance occurs.
[0083] 2-3. Temper
[0084] Temper may be performed on an O material or may be performed
on an H1n material or an H2n material.
[0085] 3. Production Method
[0086] 3-1. Heating Conditions after Casting
[0087] In the fin material according to the present embodiment, the
sizes of Si particles present in the vicinity of the surface layer
are limited. Coarse dispersed particles in a material are known to
be greatly influenced by a cooling rate in casting. It is
particularly known that since the rate of diffusion of dispersed
particles containing Fe or Mn is low, a cooling rate in casting
greatly influences the sizes of the dispersed particles, and the
higher the cooling rate in the casting is, the finer the particles
are.
[0088] In contrast, Si particles are known to be finely generated
during casting by a slight amount of an additional element such as
Sr or Na. In the fin material according to the present embodiment,
however, the distribution of Si particles in the vicinity of the
surface layer is important, and the distribution of the Si
particles is relatively greatly affected by retention time at high
temperature in a production step after casting because the rate of
the diffusion of Si in Al is relatively high. Therefore, in any
case of a DC casting method and a continuous casting method, when
retention is performed at a temperature of 530.degree. C. or more
in a production step after casting, the time of the retention is
set to 10 hours or less. In a still more preferred heating
condition, a retention time in the case of performing retention at
a temperature of 520.degree. C. or more is set to 0 to 10 hours.
Here, a retention time of 0 hour means that retention is stopped
immediately after a predetermined retention temperature has been
reached. The restrictions of such heating conditions enable all Si
particles that are present in the range of the length W in the
whole cross section of the fin material and satisfy D.gtoreq.L and
L+D>0.04 t to satisfy 0.ltoreq..SIGMA..pi.D.sup.2<0.08 tW. In
contrast, in the case of retention at a temperature of 530.degree.
C. or more for more than 10 hours, coarsening due to Ostwald growth
significantly occurs. As a result, the number of Si particles which
satisfy D.gtoreq.L and L+D>0.04 t in the Si particles in the
surface layer and the equivalent circle diameter of each Si
particle are increased, whereby 0.ltoreq..SIGMA..pi.D.sup.2<0.08
tW is not satisfied.
[0089] 3-2. In Case of DC Casting
[0090] A method for producing the aluminum alloy material used in
the present embodiment may be performed according to a usual
method, and it is necessary to note the heating conditions
described above. An example of the production method in the case of
DC casting will be described below. The rate of casting a slab in
casting is controlled as described below. The casting rate
influences a cooling rate and is therefore set to 20 to 100
min/min. When the casting rate is less than 20 mm/min, it is
impossible to obtain a sufficient cooling rate, and crystallized
products such as Si-based particles and an Al--Fe--Mn--Si-based
intermetallic compound are coarsened. In contrast, when the casting
rate is more than 100 mm/min, an aluminum alloy material is not
sufficiently solidified in casting, and it is impossible to obtain
a normal ingot. The casting rate is preferably 30 to 80 mm/min. The
casting rate can be adjusted depending on the composition of the
produced alloy material in order to obtain the characteristic metal
structure of the present embodiment. The cooling rate depends on
the cross-sectional shape of the slab, such as a thickness or a
width, and a cooling rate of 0.1 to 2.degree. C./s can be achieved
in the center of an ingot by setting the casting rate to 20 to 100
mm/min as described above. Such a cooling rate (0.1 to 2.degree.
C./s) in the center of an ingot enables the generation of coarse Si
particles to be suppressed.
[0091] The thickness of the ingot (slab) in the DC casting is
preferably 700 mm or less. When the thickness of the slab is more
than 700 mm, it is impossible to obtain such a sufficient cooling
rate as described above, and Si particles and an
Al--Fe--Mn--Si-based intermetallic compound are coarsened. The
thickness of the slab is more preferably 500 mm or less.
[0092] The slab cast by the DC casting method is subjected to a
heating step prior to hot rolling, a hot rolling step, a cold
rolling step, and an annealing step. Homogenization treatment may
be performed after the casting and before the hot rolling.
[0093] The slab produced by the DC casting method is subjected to
the heating step prior to the hot rolling, after the homogenization
treatment or without being subjected to the homogenization
treatment. It is preferable to perform the heating step according
to a usual method so that a heating and retention temperature is in
a range of 400 to 570.degree. C., preferably 450 to 520.degree. C.,
and a retention time is in a range of 0 to 15 hours, preferably 1
to 10 hours, and so that the retention time is not more than 10
hours when heating is performed to 530.degree. C. or more. A
retention temperature of less than 400.degree. C. results in the
high deformation resistance of the slab in the hot rolling and may
cause cracking to occur. In contrast, a retention temperature of
more than 570.degree. C. may cause melting to locally occur. When
the retention time is more than 15 hours, coarsening is prone to
occur due to Ostwald growth of Si particles, Ostwald growth of an
Al--Fe--Mn--Si-based intermetallic compound proceeds, precipitates
are coarsened, and the distribution of the precipitates becomes
nondense. As a result, the frequency of the generation of the
nuclei of recrystallized grains in the heating for bonding is
increased, whereby a crystal particle diameter is reduced, and
deformation is prone to occur in the heating for bonding. A
retention time of 0 hours mean that the heating is ended
immediately after the heating and retention temperature has been
reached.
[0094] Subsequently to the heating step, the slab is subjected to
the hot rolling step. The hot rolling step includes a hot rough
rolling stage and a hot finishing rolling stage. In such a case, a
total rolling reduction in the hot rough rolling stage is set to 92
to 97%, and three or more passes at a rolling reduction of 15% or
more are included in passes in the hot rough rolling.
[0095] A coarse crystallized product is generated in a final
solidification portion in the slab produced by the DC casting
method. Since a crystallized product is sheared and divided into
small portions by rolling in a step of making a sheet material, the
crystallized product is observed in a particle form after the
rolling. The hot rolling step includes: the hot rough rolling stage
in which a sheet having a certain thickness is made from the slab;
and the hot finishing rolling stage in which a sheet thickness of
about several millimeters is achieved. For dividing the
crystallized product, it is important to control a rolling
reduction in the hot rough rolling stage in which rolling from the
slab is performed. Specifically, in the hot rough rolling stage,
the rolling is performed so that the thickness of the slab is from
300 to 700 mm to about 15 to 40 mm. The coarse crystallized product
can be finely divided by setting a total rolling reduction in the
hot rough rolling stage to 92 to 97%, preferably 94 to 96%, and
allowing the hot rough rolling stage to include three or more
passes at a rolling reduction of 15% or more, preferably four or
more passes at a rolling reduction of 20% or more. As a result, Si
particles and an Al--Fe--Mn--Si-based intermetallic compound which
are crystallized products can be fragmented and can be allowed to
be in an appropriate distribution state regulated in the present
embodiment.
[0096] A total rolling reduction of less than 92% in the hot rough
rolling stage results in the insufficient effect of the
fragmentation of the crystallized product. In contrast, a total
rolling reduction of more than 97% requires the small thickness of
the finished sheet in the hot rough rolling, which is difficult for
a facility. A method in which the thickness of an original slab is
increased to increase the total rolling reduction is also
acceptable but is difficult because the thickness exceeds the upper
limit value of the thickness of the slab. A rolling reduction in
each pass in the hot rough rolling stage also affects the
distribution of the crystallized product, and the crystallized
product is divided by increasing the rolling reduction in each
pass. The case of less than three passes at a rolling reduction of
15% or more in passes in the hot rough rolling stage results in the
insufficient effect of the fragmentation of the crystallized
product. A rolling reduction of less than 15% is not targeted
because the rolling reduction is insufficient, and the crystallized
product is not fragmented. The upper limit of the number of passes
at a rolling reduction of 15% or more is not particularly regulated
but is preferably set to about ten in consideration of productivity
and the like.
[0097] In the case of the H1n temper, the hot-rolled material is
subjected to the cold rolling step after the hot rolling step. The
conditions of the cold rolling step are not particularly limited.
An annealing step in which the cold-rolled material is annealed is
performed during the cold rolling step. This intermediate annealing
is performed under the conditions in the ranges of 250 to
450.degree. C. and 1 to 5 hours, preferably 300 to 400.degree. C.
and 2 to 4 hours. After the annealing step, the rolled material is
subjected to final cold rolling to achieve a final sheet thickness.
When a working rate in the final cold rolling stage, {(sheet
thickness before working-sheet thickness after working)/sheet
thickness (%) before working}, is too high, the driving force of
recrystallization in bonding and heating is increased, and crystal
grains become small, thereby increasing deformation in the heating
for bonding. A working rate in the final cold rolling stage is
preferably set to about 10 to 30%, more preferably about 12 to 25%.
In the case of the H2n temper, after the hot rolling step, the
hot-rolled material may be worked to achieve a final sheet
thickness in the cold rolling step and may be subjected to final
annealing, or may be subjected to final annealing in an
intermediate annealing step after the final cold rolling, similarly
in the case of the H1n temper.
[0098] 3-3. In Case of Continuous Casting
[0099] The continuous casting method is not particularly limited as
long as being a method for continuously casting a sheet-shaped
ingot, such a twin-roller-type continuous casting rolling method or
a twin-belt-type continuous casting method. The twin-roller-type
continuous casting rolling method is a method in which molten
aluminum is supplied between a pair of water-cooling rolls from a
molten metal supply nozzle made of a refractory to continuously
cast and roll a thin sheet. A Hunter method, a 3C method, or the
like is known as the method. The twin-belt-type continuous casting
method is a continuous casting method in which a molten metal is
teemed between rotation belts that vertically face each other and
are water-cooled to solidify the molten metal by cooling from a
belt surface to make a slab, and the slab is continuously drawn
from a side opposite to the teeming portion of the belts and wound
in a coil form. A Hazelett method or the like is known as the
method.
[0100] A cooling rate in casting in the twin-roller-type continuous
casting rolling method is several times to several hundred times
higher than that in a semi-continuous casting method. For example,
the cooling rate in the case of the semi-continuous casting method
is 0.5 to 20.degree. C./s, whereas the cooling rate in the case of
the twin-roller-type continuous casting rolling method is 100 to
1000.degree. C./s. Therefore, there is a characteristic in that
dispersed particles generated in casting are finely and highly
densely distributed in comparison with the semi-continuous casting
method.
As a result, generation of a coarse crystallized product is
suppressed, and therefore, crystal grains in bonding and heating
are coarsened. Since the cooling rate is high, the amount of
solid-dissolved additional element can be increased. As a result,
fine precipitates are formed by subsequent heat treatment and can
contribute to coarsening of crystal grains in bonding and heating.
In the present embodiment, the cooling rate in the case of the
twin-roller-type continuous casting rolling method is preferably
set to 100 to 1000.degree. C./s, and more preferably set to 300 to
900.degree. C./s. A cooling rate of less than 100.degree. C./s
precludes obtainment of a metal structure of interest, while a
cooling rate of more than 1000.degree. C./s precludes stable
production.
[0101] The rate of a rolled sheet cast by the twin-roller-type
continuous casting rolling method is preferably 0.5 to 3 m/min and
more preferably 1 to 2 m/min. The casting rate influences a cooling
rate. When the casting rate is less than 0.5 m/min, it is
impossible to obtain such a sufficient cooling rate as described
above, and a compound is coarsened. When the casting rate is more
than 3 m/min, the aluminum alloy material is not sufficiently
solidified between the rolls during the casting, and it is
impossible to obtain a normal sheet-shaped ingot.
[0102] The temperature of the molten metal cast by the
twin-roller-type continuous casting rolling method is preferably in
a range of 650 to 800.degree. C. The temperature of the molten
metal is the temperature of a head box just in front of the molten
metal supply nozzle. A molten metal temperature of less than
650.degree. C. allows the dispersed particles of a coarse
crystallized product to be generated in the molten metal supply
nozzle and allows the dispersed particles to be mixed into the
ingot, thereby causing the sheet to be cut in the cold rolling. A
molten metal temperature of more than 800.degree. C. prevents the
aluminum alloy material from being sufficiently solidified between
the rolls in the casting, whereby it is impossible to obtain a
normal sheet-shaped ingot. The temperature of the molten metal is
more preferably 680 to 750.degree. C.
[0103] The sheet thickness of the sheet-shaped ingot cast by the
twin-roller-type continuous casting rolling method is preferably 2
to 10 mm. In the range of the thickness, a homogeneous structure in
which the solidification rate of the center of the sheet thickness
is high is easily obtained. A sheet thickness of less than 2 mm
results in the small amount of aluminum passed through a casting
machine per unit time, thereby precluding stable supply of a molten
metal in a sheet width direction. In contrast, a sheet thickness of
more than 10 mm precludes winding by the rolls. The sheet thickness
of the sheet-shaped ingot is more preferably 4 to 8 mm.
[0104] In the step of cold-rolling the sheet-shaped ingot, cast by
the twin-roller-type continuous casting rolling method, to achieve
a final sheet thickness, annealing is performed at 250 to
550.degree. C. for 1 to 10 hours, preferably at 300 to 500.degree.
C. for 2 to 8 hours, where a time for which retention at
530.degree. C. or more is performed is in a range of 10 hours or
less. The annealing may be performed in any step, except the final
cold rolling, in the production step after the casting. It is
necessary to perform the annealing one or more times. The upper
limit of the number of times of the annealing is preferably three,
more preferably two. The annealing is performed for softening the
material to facilitate the obtainment of desired material strength
in the final rolling. The size and density of the crystallized
product and the precipitate in the material, and the amount of the
solid solution of an added element can be optimally adjusted by the
annealing.
[0105] When the temperature of the annealing is less than
250.degree. C., tensile strength (TS) before brazing heating
becomes high because the material is insufficiently softened. High
TS before brazing heating results in poor moldability and therefore
in the deterioration of a core dimension, thereby resulting in the
deterioration of durability. In contrast, when the annealing is
performed at a temperature of more than 550.degree. C., the amount
of heat input into the material during the production step is too
large, and therefore, the crystallized product and the precipitate
are coarsely and sparse distributed. The coarsely and sparse
distributed crystallized product and precipitate hardly include a
solid-dissolved element and allow the amount of solid solution in
the material to be inhibited from decreasing. An annealing time of
less than 1 hour allows the above-described effects to be
insufficient, and an annealing time of more than 10 hours allows
the above-described effects to be saturated and therefore results
in economical disadvantage.
[0106] 4. Bonding Conditions
[0107] 4-1. Heating Conditions
[0108] A bonding method using the fin material according to the
present embodiment will now be described. The fin material
according to the present embodiment has the ability of being bonded
by heating with a single layer and exhibits the function of
generating a liquid phase in the material by heating and of bonding
by the liquid phase. A higher temperature at the time of heating
results in formation of a larger amount of liquid phase and
facilitates security of bondability. However, the formation of a
larger amount of liquid phase facilitates a decrease in the sheet
thickness of the fin material and the deformation of the fin
material. Therefore, it is important to manage the conditions of
the heating for bonding. Specifically, the heating is performed for
a time required for the bonding at a temperature which is not less
than a solidus line in which a liquid phase is generated in the fin
material according to the present embodiment, which is not more
than a liquidus line, and which is less than a temperature at which
the generation of the liquid phase in the fin material results in a
decrease in strength, thereby making it impossible to maintain a
shape.
[0109] For a further specific heating condition, it is necessary to
perform the bonding at a temperature at which the ratio of the mass
of a liquid phase generated in the fin material to the total mass
of the fin material (hereinafter referred to as "liquid phase
ratio") is more than 0% and 35% or less. A liquid phase ratio of
more than 0% is required because it is impossible to perform the
bonding unless the liquid phase is generated. However, since a less
liquid phase may preclude the bonding, a liquid phase ratio of 5%
or more is preferred. In contrast, a liquid phase ratio of more
than 35% results in the excessively large amount of generated
liquid phase, thereby causing the fin material to be greatly
deformed at the time of the heating for bonding and making it
impossible to maintain a shape. A liquid phase ratio of 5 to 30% is
preferred, and a liquid phase ratio of 10 to 20% is more
preferred.
[0110] For sufficiently filling the liquid phase of the fin
material between the fin material and another member bonded to the
fin material, consideration of the time of filling the liquid phase
is preferred, and a time for which the liquid phase ratio is 5% or
more is 30 to 3600 seconds. More preferably, the time for which the
liquid phase ratio is 5% or more is 60 to 1800 seconds, resulting
in further sufficient filling and reliable bonding. When the time
for which the liquid phase ratio is 5% or more is less than 30
seconds, the liquid phase may be prevented from being sufficiently
filled into a bond portion. In contrast, when the time is more than
3600 seconds, the deformation of the fin material may proceed. In
the bonding method in the present embodiment, the liquid phase
moves only in the extreme vicinity of the bond portion, and a time
required for the filling does not depend on the size of the bond
portion.
[0111] For specific examples of preferred heating conditions, a
bonding temperature may be set at 580 to 640.degree. C., and a
retention time at the bonding temperature in this range may be set
to 0 to 10 minutes, in the case of the above-described fin material
according to the present embodiment. Here, 0 minutes mean that
cooling is started immediately after the temperature of a member
has reached a predetermined bonding temperature. The
above-described retention time is more preferably 30 seconds to 5
minutes. The bonding temperature is more preferably set to 590 to
620.degree. C. For example, it is desirable to set a bonding and
heating temperature to a lower temperature of 580 to 590.degree. C.
when the content of Si is about 4 to 5%. The heating conditions may
be adjusted depending on composition in order to allow the metal
structure of the bond portion to be in a preferred state described
later.
[0112] Measurement of an actual liquid phase ratio during heating
is very difficult. Thus, a liquid phase ratio regulated in the
present embodiment can be typically determined by a lever rule on
the basis of alloy composition and maximum attainment temperature
using an equilibrium diagram. In an alloy system of which the phase
diagram has already been revealed, a liquid phase ratio can be
determined by using a lever rule with the use of the phase diagram.
In contrast, in an alloy system of which the equilibrium diagram is
not made to be public, a liquid phase ratio can be determined using
equilibrium calculation phase diagram software. A technique in
which a liquid phase ratio is determined by a lever rule with the
use of alloy composition and temperature is incorporated into the
equilibrium calculation phase diagram software. Examples of the
equilibrium calculation phase diagram software include Thermo-Calc,
manufactured by Thermo-Calc Software AB. In the alloy system of
which the equilibrium diagram has been revealed, the equilibrium
calculation phase diagram software may also be used for
simplification because the same result as the result of the
determination of a liquid phase ratio by using a lever rule on the
basis of the equilibrium diagram is given even if the liquid phase
ratio is calculated using the equilibrium calculation phase diagram
software.
[0113] 4-2. Others
[0114] A heating atmosphere in heat treatment is preferably a
non-oxidizing atmosphere replaced with nitrogen, argon, or the
like; or the like. Further favorable bondability can be obtained by
using a non-corrosive flux. Further, heating and bonding can be
performed in a vacuum and under reduced pressure.
[0115] Examples of a method for applying the non-corrosive flux
include a method in which a member to be bonded is assembled,
followed by sprinkling a flux powder on the member, and a method in
which a flux powder is suspended in water, and the flux powder with
water is spray-coated. In the case of coating the material in
advance, the adhesiveness of the coating can be enhanced by
applying a flux powder mixed with a binder such as acryl resin.
Examples of non-corrosive fluxes used for obtaining the usual
functions of the fluxes include: fluoride-based fluxes such as
KAlF.sub.4, K.sub.2AlF.sub.5, K.sub.2AlF.sub.5.H.sub.2O,
K.sub.3AlF.sub.6, AlF.sub.3, KZnF.sub.3, and K.sub.2SiF.sub.6; and
cesium-based fluxes such as Cs.sub.3AlF.sub.6,
CsAlF.sub.4.2H.sub.2O, and Cs.sub.2AlF.sub.5.H.sub.2O.
[0116] 5. Metal Structure after Bonding
[0117] In the fin material according to the present embodiment, a
crystal particle diameter after bonding and heating is preferably
set to 50 .mu.m or more, and more preferably set to 200 .mu.m or
more, in order to suppress deformation (warpage or buckling) in the
heating for bonding. When the crystal particle diameter is less
than 50 .mu.m, grain boundary sliding may occur, thereby resulting
in significant deformation, in bonding and heating. When the
crystal particle diameter is 50 .mu.m or more, deformation in the
heating for bonding is suppressed, and therefore, a clearance
between the fin material and another member such as a tube is
appropriately maintained, whereby bondability can be improved. The
upper limit value of the crystal particle diameter is not
particularly limited but depends on alloy composition and a
production method, and is about 2000 .mu.m in the present
embodiment.
[0118] 6. Application to Clad Material
[0119] The fin material according to the present embodiment has a
feature in that a decrease in sheet thickness is suppressed by
controlling a metal structure in the vicinity of a surface layer.
Such an effect can also be obtained similarly in the case of
cladding the fin material according to the present embodiment on
another material. In such a case, a decrease in sheet thickness is
up to 8% or less of the thickness of the clad fin material portion
according to the present embodiment, thereby therefore achieving
the less rate of the decrease in sheet thickness with respect to
the sheet thickness of the whole clad material. Thus, a cladding
ratio is not particularly limited, and may be in a range enabling
production. Specifically, the cladding ratio is about 2% to 98%,
preferably about 5 to 95%, depending on the sheet thickness of the
clad material.
[0120] Examples of such clad materials include an aluminum alloy
brazing sheet in which the fin material according to the present
embodiment is clad as a skin material on one surface or both
surfaces of a core material made of an aluminum alloy. For example,
1000-series pure aluminum, or an aluminum alloy such as a
3000-series or 6000-series aluminum alloy is used as the core
material.
[0121] 7. Application to Heat Exchanger
[0122] Since a decrease in sheet thickness is suppressed in the fin
material according to the present embodiment, the application of
the fin material to a heat exchanger results in improvement in
bondability. For example, plural notch grooves 16 opened to
penetrate the same positions of a plate-shaped fin material are
disposed at a predetermined spacing along each end edge of many
sheet-shaped fins 12 which overlap one another at a predetermined
spacing, as illustrated in FIGS. 1 and 2. Collars 20 are formed
about the notch grooves 16 so as to come in contact with surfaces
of flat tubes 14 including flow passages 15 through which a
heat-transfer fluid is allowed to flow. The flat tubes 14 are
assembled in the state of extending in the direction of overlapping
such sheet-shaped fins 12 by fitting each of the flat tubes 14 into
each of the notch grooves 16 at the same positions, bonded, and
heated, whereby a heat exchanger 10 is produced. The heat exchanger
may be produced by heating and bonding the fin material according
to the present embodiment, worked in a wave (corrugated) shape,
between the flat tubes which are arranged at a predetermined pacing
so that flat portions face each other, and through which the
heat-transfer fluid flows.
Examples
[0123] Preferred embodiments of the present disclosure will be
specifically described below based on Examples and Comparative
Examples. However, the present disclosure is not limited
thereto.
[0124] First, test materials having a thickness of 400 mm, a width
of 1000 mm, and a length of 3000 mm were cast by a DC casting
method using aluminum alloys having alloy compositions A1 to A23
set forth in Table 1. A casting rate was set to 50 mm/min at a
cooling rate set to 1.degree. C./s. In the alloy compositions in
Table 1, "-" indicates a value that is not more than a detection
limit, and "balance" includes inevitable impurities. Then, the
ingot cast by the DC casting method was faced to have a thickness
of 380 mm, then heated to a temperature of 480.degree. C. in a
heating and retention step prior to hot rolling, retained at the
temperature for 5 hours, and then subjected to a hot rolling step.
In the hot rolling step, the ingot was rolled to have a thickness
of 3 mm. A total rolling reduction in hot rough rolling in the hot
rolling step was 92.5%, and three or more passes at a rolling
reduction of 15% or more in each pass in the hot rough rolling were
performed. In a subsequent cold rolling step, the rolled sheet was
rolled to have thickness of 0.09 mm. Further, the rolled material
was subjected to an intermediate annealing step at 380.degree. C.
for 2 hours and finally rolled to have a final sheet thickness of
0.07 mm in a final cold rolling stage, thereby obtaining a sample
material. A working rate in the final cold rolling stage was
22.2%.
TABLE-US-00001 TABLE 1 Alloy Composition (mass %) Al and inevitable
Alloy Designation Si Fe Cu Mn Zn impurities A1 1.70 -- -- -- --
Balance A2 3.70 -- -- -- -- Balance A3 4.80 -- -- -- -- Balance A4
1.00 -- -- -- -- Balance A5 5.50 -- -- -- -- Balance A6 2.50 0.05
0.08 1.00 -- Balance A7 2.50 0.60 0.08 1.00 -- Balance A8 2.50 1.50
0.08 1.00 -- Balance A9 2.50 0.25 0.08 1.00 -- Balance A10 2.50
0.25 0.50 1.00 -- Balance A11 2.50 0.25 1.40 1.00 -- Balance A12
2.50 0.25 0.08 0.08 -- Balance A13 2.50 0.25 0.08 0.50 -- Balance
A14 2.50 0.25 0.08 1.80 -- Balance A15 2.50 0.25 0.08 1.00 0.08
Balance A16 2.50 0.25 0.08 1.00 0.50 Balance A17 2.50 0.25 0.08
1.00 1.00 Balance A18 2.50 0.25 0.08 1.00 3.00 Balance A19 2.50
0.25 0.08 1.00 4.80 Balance A20 2.50 0.25 0.08 1.00 6.50 Balance
A21 2.50 2.50 0.08 1.00 1.50 Balance A22 2.50 0.25 2.00 1.00 1.50
Balance A23 2.50 0.25 0.08 2.50 1.50 Balance B1 0.05 0.15 0.40 0.15
-- Balance C1 10.00 0.25 -- -- -- Balance C2 0.05 0.50 0.08 1.10 --
Balance C3 2.50 0.25 -- -- -- Balance
[0125] A sample material with the alloy composition A2, heated to a
temperature of 520.degree. C. after DC casting and retained at the
temperature for 10 hours in a different manner from the manner
described above, was produced (DC2 of Example 19 in Table 2
described later). In addition, a sample material with the alloy
composition A3, heated to a temperature of 540.degree. C. after DC
casting and retained at the temperature for 15 hours in a different
manner from the manner described above, was produced (DC3 of
Comparative Example 1 in Table 2 described later). Then, the test
material was subjected to the hot rolling step. In the hot rolling
step, the test material was rolled to have a thickness of 3 mm. A
total rolling reduction in hot rough rolling in the hot rolling
step was 92.5%, and three or more passes at a rolling reduction of
15% or more in each pass in the hot rough rolling were performed.
In a subsequent cold rolling step, the rolled sheet was rolled to
have thickness of 0.09 mm. Further, the rolled material was
subjected to an intermediate annealing step at 380.degree. C. for 2
hours and finally rolled to have a final sheet thickness of 0.07 mm
in a final cold rolling stage, thereby obtaining a sample material.
A working rate in the final cold rolling stage was 22.2%.
[0126] In addition, an ingot with the component of A17 was also
cast by a twin-roller-type continuous casting rolling method in a
different manner from the manner described above. The temperature
of a molten metal cast by the twin-roller-type continuous casting
rolling method was 650 to 800.degree. C., and the thickness of a
cast metal sheet was 6 mm. A casting rate was set to 700 mm/min at
a cooling rate set to 200.degree. C./s. Then, the obtained
sheet-shaped ingot was cold-rolled to 0.7 mm, subjected to
intermediate annealing at 480.degree. C. for 5 hours, then
cold-rolled to 0.09 mm, subjected to the second annealing at
380.degree. C. for 2 hours, and then cold-rolled to 0.070 mm,
thereby obtaining a sample material.
[0127] Further, C1, C2, and C3 in Table 1 are cast by a DC casting
method in a manner similar to the manner for Al to A23 and
subjected to a heating and retention step prior to hot rolling.
Then, C1 and C3 were put on both surfaces of C2, respectively, at a
cladding ratio of 10% and hot-clad-rolled to produce clad materials
CL1 (C1/C2/C1) and CL2 (C3/C2/C3). In a hot clad rolling step, the
rolling was performed to achieve a thickness of 3 mm. A total
rolling reduction in hot rough rolling in the hot clad rolling step
was 93.8%, and three or more passes at a rolling reduction of 15%
or more in each pass in the hot rough rolling were performed. In a
subsequent cold rolling step, the rolled sheet was rolled to have
thickness of 0.09 mm. Further, the rolled material was subjected to
an intermediate annealing step at 380.degree. C. for 2 hours and
finally rolled to have a final sheet thickness of 0.07 mm in a
final cold rolling stage, thereby obtaining a sample material. A
working rate in the final cold rolling stage was 22.2%.
[0128] The sample materials produced as described above were
evaluated as described below.
[0129] <Productability>
[0130] First, productability in a production process was evaluated.
In a method for evaluating the productability, a case in which no
problem occurred and a favorable sheet material or slab was
obtained in the production process when the sheet material or slab
was produced was evaluated as "good", while a case in which
cracking occurred in casting or a case in which the generation of a
big crystallized product in the casting caused rolling to be
precluded and productability was problematic was evaluated as
"fair".
[0131] The results are set forth in Table 2.
TABLE-US-00002 TABLE 2 Evaluation Decrease in Sheet Tensile
Examples/Comparative Alloy Production Metal Thickness Test
Bondability Corrosion Examples Designation Method Productability
Structure (%) (MPa) (%) Resistance Example 1 A1 DC Good 0.006 3 95
100 Fair Example 2 A2 DC Good 0.012 5 110 76 Fair Example 3 A3 DC
Good 0.016 7 121 60 Fair Example 4 A6 DC Good 0.007 3 141 100 Fair
Example 5 A7 DC Good 0.007 3 139 100 Fair Example 6 A8 DC Good
0.007 3 145 100 Fair Example 7 A9 DC Good 0.007 3 139 100 Fair
Example 8 A10 DC Good 0.007 3 159 100 Fair Example 9 A11 DC Good
0.007 3 206 100 Fair Example 10 A12 DC Good 0.008 4 113 100 Fair
Example 11 A13 DC Good 0.008 4 123 100 Fair Example 12 A14 DC Good
0.006 3 167 100 Fair Example 13 A15 DC Good 0.007 3 143 100 Fair
Example 14 A16 DC Good 0.007 3 141 100 Good Example 15 A17 DC Good
0.007 3 139 100 Good Example 16 A18 DC Good 0.007 3 141 100
Excellent Example 17 A19 DC Good 0.007 3 142 100 Excellent Example
18 A17 CC Good 0.006 3 154 100 Good Example 19 A2 DC2 Good 0.014 6
108 75 Good Example 20 CL2 DC Good 0.008 4 107 100 Fair Comparative
Example 1 A3 DC3 Good 0.018 8 95 53 Fair Comparative Example 2 A4
DC Good 0.003 2 92 0 Fair Comparative Example 3 A5 DC Good 0.018 9
125 51 Fair Comparative Example 4 CL1 DC Good 0.033 15 164 40 Fair
Comparative Example 5 A20 DC Good 0.007 3 141 100 Poor Comparative
Example 6 A21 DC Fair 0.007 -- -- -- -- Comparative Example 7 A22
DC Fair 0.007 -- -- -- -- Comparative Example 8 A23 DC Fair 0.005
-- -- -- --
[0132] <Metal Structure>
[0133] Then, the metal structures prior to the bonding and heating
of the sample materials were evaluated. A cross section along the
thickness direction of each sample material was polished, and a
photograph of an SEM observation image was taken. An equivalent
circle diameter D and a distance L from a surface layer were
measured by the image analysis of the SEM observation image in the
area region of the whole portion (t.times.W (W: 3 mm)) of the cross
section, only Si particles satisfying D.gtoreq.L and D+L>0.04 t
were chosen, and the total (.SIGMA..pi.D.sup.2) of .pi.D.sup.2 of
the Si particles was calculated. In the present Examples, the
regulation of the present disclosure is satisfied if
.SIGMA..pi.D.sup.2 is less than 0.08 tW=0.08.times.0.07
(mm).times.3 (mm)=0.017 (mm.sup.2). The results of calculated
.SIGMA..pi.D.sup.2 (mm.sup.2) for the metal structures are set
forth in Table 2.
[0134] <Decrease in Sheet Thickness>
[0135] The rate of decrease in the sheet thickness of the sample
material in the case of heating at a temperature equivalent to a
bonding and heating temperature was evaluated. In such a case, fin
sheet thicknesses before and after the heating were measured with a
micrometer. In such a case, the rate of decrease in sheet thickness
was calculated with the arithmetic mean value of measured sheet
thicknesses at the same three or more positions before and after
the heating in order to measure a difference before and after the
heating. For the heating operation, each sample material was cut to
have a length of 100 mm and a width of 20 mm, a hole was made in
one end in a longitudinal direction, a stainless steel wire was
passed through the hole, and the sample material was heated to
600.degree. C. and retained for 3 minutes in a state in which a
stand was hung with the wire. In the present Examples and
Comparative Examples, a decrease in sheet thickness of less than 8%
was regarded as acceptable. The results are set forth in Table 2. A
decrease (%) in sheet thickness set forth in Table 2 is defined as
a value obtained by discarding digits to the right of the decimal
point of an actually determined numerical value.
[0136] <Tensile Test>
[0137] A tensile test on each sample material before bonding and
heating was conducted. The tensile test on each sample material was
conducted at ordinary temperature according to JIS Z2241 under
conditions of a tension speed of 10 mm/min and a gauge length of 50
mm. The results are set forth in Table 2.
[0138] <Bondability>
[0139] Then, bondability was evaluated. As illustrated in FIG. 1,
each test material was cut to have a width of 20 mm and a length of
100 mm, and a fin material including notches having a width of 2 mm
and a length of 15 mm at a pitch of 10 mm was made by pressing. As
illustrated in the cross-sectional view of FIG. 1, collars were
perpendicularly cut and raised to have a height of 0.5 mm in the
notches of the fin material. Such twenty fin materials were aligned
in parallel at a pitch of 2 mm so that the positions of the notches
were uniform. Multi-port tubes having the composition of B1 set
forth in Table 1 were inserted into the notches. Such a multi-port
tube was set to have a thickness of 1.98 mm, a width of 20 mm, and
a length of 60 mm. The twenty fins and the ten multi-port tubes
were incorporated in combination into a stainless steel jig to
produce a test piece (mini core).
[0140] The mini core produced as described above was dipped in a
10% suspension of a non-corrosive fluoride-based flux, dried, then
heated to 600.degree. C. in a nitrogen atmosphere, and retained for
3 minutes, thereby heating and bonding the fin materials and the
multi-port tubes.
[0141] After the heating and bonding of the fin materials and the
multi-port tubes, the fins were removed from the multi-port tubes,
and the states of the twenty bond portions between the multi-port
tubes and the fins of the mini-core were examined. The rate
(bonding rate) of points where the bond portions had been
completely bonded was measured. In the present Examples and
Comparative Examples, a bonding rate of 60% or more was regarded as
acceptable. The results are sets forth in Table 2.
[0142] <Corrosion Resistance>
[0143] Further, the corrosion resistance of the mini core produced
as described above was evaluated. A CASS test was conducted for 500
h to confirm the corrosion states of the multi-port tubes. The
depth of the corrosion of a maximum corrosion portion was measured
by a focal method with a microscope, a depth of 50 .mu.m or less
was regarded as excellent, a depth of more than 50 .mu.m and 150
.mu.m or less was regarded as good, a depth of more than 150 .mu.m
and 300 .mu.m or less was regarded as fair, and a depth of more
than 300 .mu.m was regarded as poor. The results are set forth in
Table 2.
[0144] As set forth in Table 2, productability, a decrease in sheet
thickness, a tensile test, bondability, and corrosion resistance
were favorable in the compositions and metal structures of the
aluminum alloy materials in Examples 1 to 20 including the
conditions regulated in the present disclosure.
[0145] In contrast, in Comparative Example 1, the metal structure
of the fin material did not satisfy the regulations, and therefore,
a decrease in sheet thickness of more than 8% and bad bondability
were exhibited.
[0146] In Comparative Example 2, the Si component in the fin
material was less than 1.50%, and therefore, an insufficient liquid
phase ratio and bad bondability were exhibited.
[0147] In Comparative Example 3, the Si component in the fin
material was more than 5.00%, therefore, the metal structure did
not satisfy the regulations, and a decrease in sheet thickness of
more than 8% and bad bondability were exhibited.
[0148] In Comparative Example 4, the content of Si in the fin
material (C1) used in the skin material of the clad material was
high, therefore, the metal structure did not satisfy the
regulations, and a decrease in sheet thickness of more than 8% and
bad bondability were exhibited.
[0149] In Comparative Example 5, the Zn component in the fin
material was more than 6.00%, and therefore, deteriorated
self-corrosion resistance and bad corrosion resistance were
exhibited.
[0150] In Comparative Examples 6 to 8, the content of each of the
Fe, Cu, and Mn components in the fin materials was large,
therefore, coarse crystallized products were formed in the casting,
and productability was problematic.
[0151] The foregoing describes some example embodiments for
explanatory purposes. Although the foregoing discussion has
presented specific embodiments, persons skilled in the art will
recognize that changes may be made in form and detail without
departing from the broader spirit and scope of the invention.
Accordingly, the specification and drawings are to be regarded in
an illustrative rather than a restrictive sense. This detailed
description, therefore, is not to be taken in a limiting sense, and
the scope of the invention is defined only by the included claims,
along with the full range of equivalents to which such claims are
entitled.
[0152] This application claims the benefit of Japanese Patent
Application No. 2016-79933, filed on Apr. 12, 2016, and Japanese
Patent Application No. 2017-60744, filed on Mar. 27, 2017, of which
the entirety of the disclosures is incorporated by reference
herein.
INDUSTRIAL APPLICABILITY
[0153] According to the present disclosure, an aluminum alloy fin
material which has high bondability and high rigidity, of which the
thickness can be reduced, and of which the reduction in the weight
is achieved, a brazing sheet in which the aluminum alloy fin
material is used, and a heat exchanger in which the fin material or
the brazing sheet is used in a fin are provided as described
above.
REFERENCE SIGNS LIST
[0154] 10 Heat exchanger [0155] 12 Sheet-shaped fin [0156] 14 Flat
tube [0157] 15 Flow passage [0158] 16 Notch groove [0159] 20
Collar
* * * * *