U.S. patent application number 10/540572 was filed with the patent office on 2006-11-02 for aluminum pipe and process for producing same.
This patent application is currently assigned to SHOWA DENKO K.K.. Invention is credited to Kazuyuki Takahashi.
Application Number | 20060243360 10/540572 |
Document ID | / |
Family ID | 32716319 |
Filed Date | 2006-11-02 |
United States Patent
Application |
20060243360 |
Kind Code |
A1 |
Takahashi; Kazuyuki |
November 2, 2006 |
Aluminum pipe and process for producing same
Abstract
An inlet pipe 6 and an outlet pipe 7 for use in condensers are
made from an alloy containing 0.90 to 1.50 mass % of Mn, and the
balance Al and inevitable impurities. The inlet pipe 6 and the
outlet pipe have an electrical conductivity of 30 to 43% IACS. The
inlet pipe 6 and an outlet pipe 7 are each produced from a pipe
blank made from an alloy containing 0.90 to 1.50 mass % of Mn, and
the balance Al and inevitable impurities, by holding the pipe blank
heated at 550 to 600 C in the atmosphere or in an inert gas
atmosphere for 10 to 600 minutes and thereafter cooling the pipe
blank. The inlet pipe 6 and the outlet pipe 7 can be produced
easily at a low cost and have satisfactory resistance to pitting
corrosion.
Inventors: |
Takahashi; Kazuyuki;
(Oyama-shi, JP) |
Correspondence
Address: |
C. IRVIN MCCLELLAND;OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
SHOWA DENKO K.K.
13-9, Shiba Daimon 1-chome, Minato-ku
Tokyo
JP
105-8518
|
Family ID: |
32716319 |
Appl. No.: |
10/540572 |
Filed: |
December 26, 2003 |
PCT Filed: |
December 26, 2003 |
PCT NO: |
PCT/JP03/16921 |
371 Date: |
June 24, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60440628 |
Jan 17, 2003 |
|
|
|
Current U.S.
Class: |
148/698 |
Current CPC
Class: |
F28F 9/0256 20130101;
C22F 1/04 20130101; F28F 21/084 20130101; F28F 9/0246 20130101;
C22C 21/00 20130101 |
Class at
Publication: |
148/698 |
International
Class: |
C22F 1/04 20060101
C22F001/04 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 27, 2002 |
JP |
2002-380756 |
Claims
1. An aluminum pipe made from an alloy containing 0.90 to 1.50 mass
% of Mn, and the balance Al and inevitable impurities, the pipe
having an electrical conductivity of 30 to 43% IACS.
2. An aluminum pipe according to claim 1 wherein Cu is contained as
an inevitable impurity, and the content of Cu is up to 0.05 mass
%.
3. An aluminum pipe according to claim 1 wherein Fe is contained as
an inevitable impurity, and the content of Fe is up to 0.25 mass
%.
4. An aluminum pipe according to claim 1 wherein Si is contained as
an inevitable impurity, and the content of Si is up to 0.25 mass
%.
5. A process for producing an aluminum pipe characterized in that a
pipe blank made from an alloy containing 0.90 to 1.50 mass % of Mn,
and the balance Al and inevitable impurities is held heated at 550
to 600.degree. C. in the atmosphere or in an inert gas atmosphere
for 10 to 600 minutes and thereafter cooled.
6. A process for producing an aluminum pipe according to claim 5
wherein the alloy for making the pipe blank contains Cu as an
inevitable impurity, and the content of Cu is up to 0.05 mass
%.
7. A process for producing an aluminum pipe according to claim 5
wherein the alloy for making the pipe blank contains Fe as an
inevitable impurity, and the content of Fe is up to 0.25 mass
%.
8. A process for producing an aluminum pipe according to claim 5
wherein the alloy for making the pipe blank contains Si as an
inevitable impurity, and the content of Si is up to 0.25 mass
%.
9. A process for producing an aluminum pipe according to claim 5
wherein the rate of rise of temperature for the heating is 20 to
130.degree. C./min.
10. A process for producing an aluminum pipe according to claim 5
wherein the rate of cooling after the heating is at least
47.degree. C./min.
11. A heat exchanger for use in motor vehicles which has an inlet
pipe and an outlet pipe each comprising an aluminum pipe according
to any one of claims 1 to 4.
12. A vehicle provided with a motor vehicle air conditioner
comprising a refrigeration cycle wherein a chlorofluorocarbon
refrigerant is used and which has a compressor, a condenser and an
evaporator, the condenser being a heat exchanger according to claim
11.
13. A refrigeration cycle wherein a chlorofluorocarbon refrigerant
is used and which has a compressor, a condenser and an evaporator,
the compressor, the condenser and the evaporator being
interconnected by piping comprising an aluminum pipe according to
any one of claims 1 to 4.
14. A vehicle wherein a refrigeration cycle according to claim 13
is installed as a motor vehicle air conditioner.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is an application filed under 35 U.S.C.
.sctn.111 (a) claiming the benefit pursuant to 35 U.S.C.
.sctn.119(e) (1) of the filing date of Provisional Application No.
60/440, 628 filed Jan. 17, 2003 pursuant to 35 U.S.C.
.sctn.111(b).
TECHNICAL FIELD
[0002] The present invention relates to aluminum pipes, and more
particularly to aluminum pipes useful as inlet pipes and outlet
pipes in heat exchanges, such as condensers or evaporators for
motor vehicle air conditioners wherein a chlorofluorocarbon
refrigerant is used, gas coolers or evaporators for motor vehicle
air conditioners wherein CO.sub.2 refrigerant is used, motor
vehicle oil coolers and motor vehicle radiators; as pipes for
piping in motor vehicle air conditioners which have a refrigeration
cycle adapted for use with a chlorofluorocarbon refrigerant, the
refrigeration cycle comprising a compressor, condenser and
evaporator which are interconnected by the piping; and as pipes for
piping in motor vehicle air conditioners which have a refrigeration
cycle adapted for use with CO.sub.2 refrigerant, the refrigeration
cycle comprising a compressor, gas cooler, intermediate heat
exchanger, expansion valve and evaporator which are interconnected
by the piping, and also to a process for producing such pipes.
[0003] The term "aluminum" as used herein and in the appended
claims includes aluminum alloys in addition to pure aluminum.
Incidentally, the metal represented by an atomic symbol of course
does not include alloys thereof.
BACKGROUND ART
[0004] Condensers are known for use in motor vehicle air
conditioners comprising a refrigeration cycle wherein a
chlorofluorocarbon refrigerant is used. Such condensers comprise a
pair of aluminum headers arranged in parallel as spaced apart from
each other, parallel flat heat exchange tubes made of aluminum and
joined at their opposite ends to the headers, a corrugated aluminum
fin disposed in an air passage clearances between each pair of
adjacent heat exchange tubes and brazed to the pair of heat
exchange tubes, an inlet pipe of aluminum connected to one of the
headers and an outlet pipe of aluminum connected to the other
header.
[0005] The inlet pipe and the outlet pipe of the condenser
described are conventionally produced, for example, from JIS A1100,
JIS A3003 or an alloy containing 1.0 to 1.5 wt. % of Mn, at least
0.2 wt. % to less than 0.6 wt. % of Mg, and the balance Al and
inevitable impurities (see the publication of JP-B No.
1991-22459).
[0006] Also known is an aluminum pipe which is adapted for use in
piping for motor vehicle air conditioners for interconnecting the
compressor, condenser and evaporator thereof and which is made from
an alloy comprising 0.3 to 1.5 mass % of Mn, up to 0.20 mass % of
Cu, 0.06 to 0.30 mass % of Ti, 0.01 to 0.20 mass % of Fe, 0.01 to
0.20 mass % of Si, and the balance Al and inevitable impurities,
the matrix of the alloy containing particles of Si compounds, Fe
compounds and Mn compounds which include up to 2.times.10.sup.4
particles, not smaller than 0.5 .mu.m in size, per square
millimeter (see the publication of JP-A No. 2002-180171).
[0007] Conventionally, a chromate surface treatment has been
conducted for heat exchange tubes and inlet and outlet pipes for
the condensers and evaporators of motor vehicle air conditioners
and pipes of aluminum piping for motor vehicle air conditioners
mentioned above in order to give improved corrosion resistance to
the tubes and pipes, whereas the treatment involves cumbersome
work. Moreover Cr.sup.6+ is a harmful substance, and the resulting
liquid waste requires a troublesome treatment. Accordingly,
condensers, evaporators and piping have the problem of
necessitating troublesome work for production. Additionally, the
use of Cr.sup.6+ is to be prohibited in Europe in the near
future.
[0008] Thus, studies are under way on treatments of condenser or
evaporator heat exchange tubes to be conducted as substitutes for
the chromate treatment wherein harmful Cr.sup.6+ is used, for
giving resistance to pitting corrosion and on tubes having
resistance to pitting corrosion.
[0009] However, inlet and outlet pipes and pipes for piping which
can be produced with ease at a lost cost and which have
satisfactory resistance to pitting corrosion still remain to be
developed. Of course, pitting corrosion resistance can not be
expected of the piping disclosed in the above two publications
unless the pipes are subjected to the chromate treatment.
[0010] An object of the present invention is to overcome the above
problems and to provide an aluminum pipe which can be produced
easily and inexpensively and which has satisfactory resistance to
pitting corrosion, and also a process for producing the pipe.
DISCLOSURE OF THE INVENTION
[0011] The present invention provides an aluminum pipe made from an
alloy containing 0.90 to 1.50 mass % of Mn, and the balance Al and
inevitable impurities, the pipe having an electrical conductivity
of 30 to 43% IACS.
[0012] With the aluminum pipe of the present invention, Mn produces
an effect to give the pipe improved resistance to pitting corrosion
and an improved strength. If the Mn content is less than 0.90 mass
%, this effect is not available. If more than 1.50 mass % of Mn is
present, the effect to give an improved strength levels off, while
hot working involves increased resistance to deformation to result
in impaired workability, for example, lower extrudability, when the
pipe is to be produced. Accordingly, the Mn content of the alloy
for making the pipe should be 0.90 to 1.50 mass %, and is
preferably 1.0 to 1.2 mass %.
[0013] If the aluminum pipe of the invention is less than 30% IACS
in electrical conductivity, the Mn content is insufficient to
result in a lower strength, whereas if the conductivity is over 43%
IACS, sufficient amounts of solid solutions of Mn and inevitable
impurities will not be formed to entail lower corrosion resistance.
Accordingly, the alloy for making the aluminum pipe should be 30 to
43% IACS, and is preferably 33 to 37% IACS, in electrical
conductivity.
[0014] Since the aluminum pipe of the invention is 30 to 43% IACS
in electrical conductivity, the pipe can be prevented from pitting
without being subjected to any chromate treatment. Further because
the pipe is made from an alloy containing 0.90 to 1.50 mass % of Mn
and the balance Al and inevitable impurities, the pipe has an
improved strength and can be produced with high workability.
Moreover, the pipe can be produced merely by holding a pipe blank
heated at a predetermined temperature in the atmosphere or in an
inert gas atmosphere for a predetermined period of time and
thereafter cooling the blank. The pipe can therefore be produced
easily at a lost cost.
[0015] When the aluminum pipe of the invention contains Cu as an
inevitable impurity, the content of Cu as such an impurity is
preferably up to 0.05 mass % since Cu as an inevitable impurity is
likely to give the aluminum pipe impaired resistance to pitting
corrosion even if present in a very small amount. Thus, the Cu
content is preferably up to 0.05 mass %.
[0016] In the case where the aluminum pipe of the invention
contains Fe as an inevitable impurity, the content of Fe as such an
impurity is preferably up to 0.25 mass. % because Fe as an
inevitable impurity is likely to give the aluminum pipe impaired
resistance to pitting corrosion although less influential than Cu.
Accordingly, the Fe content is preferably up to 0.25 mass %.
[0017] In the case where the aluminum pipe of the invention
contains Si as, an inevitable impurity, the content of Si is
preferably up to 0.25 mass % as an inevitable impurity because Si
as such an impurity, like Fe, has the likelihood of giving the
aluminum pipe lower resistance to pitting corrosion. Accordingly,
the Si content is preferably up to 0.25 mass %.
[0018] The process of the invention for producing an aluminum pipe
is characterized in that a pipe blank made from an alloy containing
0.90 to 1.50 mass % of Mn, and the balance Al and inevitable
impurities is held heated at 550 to 600.degree. C. in the
atmosphere or in an inert gas atmosphere for 10 to 600 minutes and
thereafter cooled.
[0019] According to the aluminum pipe production process of the
present invention, the pipe blank is held heated at the specified
temperature for the specified period of time, thereby permitting
the Mn and inevitable impurities in the alloy making the pipe blank
to form solid solutions in the matrix, whereby the crystals and
precipitates contained in the material and serving as nuclei for
causing corrosion are diminished to give improved corrosion
resistance. This results in a lower electrical conductivity and
imparts improved resistance to pitting corrosion to the aluminum
pipe produced. The heating temperature is 550 to 600.degree. C.
because if the temperature is lower than 550.degree. C., sufficient
quantities of solid solutions of Mn and inevitable impurities will
not be formed in the matrix, and further because if the temperature
is over 600.degree. C., an economically poor efficiency only will
result with no improvement achieved in the effect to form solid
solutions of Mn and inevitable impurities in the matrix. The blank
is held heated for 10 to 600 minutes because if the period is less
than 10 minutes, solid solutions of Mn and inevitable impurities
will not be formed satisfactorily in the matrix, and further
because if the period is in excess of 600 minutes, an economically
poor efficiency only will result with no improvement achieved in
the effect to form solid solutions of Mn and inevitable impurities
in the matrix.
[0020] The production process of the invention produces the
aluminum pipe described above relatively easily at a lost cost.
[0021] In the aluminum pipe production process of the invention,
the alloy for making the pipe blank is the same as that of the
aluminum pipe of the invention with respect to the Mn content and
the contents of Cu, Fe and Si as inevitable impurities in the
alloy.
[0022] With the aluminum pipe production process of the invention,
the rate of rise in temperature for heating is preferably 20 to
130.degree. C./min. The reason is that if the rate of rise in
temperature is less than 20.degree. C./min, an economically
impaired efficiency will result, and that if the rate is in excess
of 130.degree. C./min, it is likely that other products, such as
aluminum tubes, to be heated along with the present aluminum pipe
will not be heated at a uniform rate of rise in temperature.
[0023] In the aluminum pipe production process of the invention,
the pipe blank heated is thereafter cooled preferably at a rate of
at least 47.degree. C./min because if the cooling rate is less than
47.degree. C./min, Mn and inevitable impurities dissolved in the
matrix in the form of solid solutions will separate out again to
possibly result in impaired corrosion resistance.
[0024] When the pipe blank is heated at the above rate of rise of
temperature and/or cooled at the above rate, an economically high
efficiency can be achieved, and the aluminum pipe produced is
reliably given resistance to pitting corrosion.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] FIG. 1 is a perspective view showing a condenser which has
an inlet pipe and an outlet pipe each comprising an aluminum pipe
of the invention and which is adapted for use in motor vehicle air
conditioners wherein a chlorofluorocarbon refrigerant is used. FIG.
2 is a diagram showing a heating pattern in Examples 1 to 4.
BEST MODE OF CARRYING OUT THE INVENTION
[0026] An embodiment of the invention will be described below with
reference to the drawing.
[0027] With reference to FIG. 1, a condenser 1 for use in motor
vehicle air conditioners wherein a chlorofluorocarbon refrigerant
is used comprises a pair of aluminum headers 2, 3 arranged in
parallel and spaced apart from each other, parallel flat
refrigerant tubes 4 (heat exchange tubes) made of aluminum
extrudate and each joined at its opposite ends to the two headers
2, 3, corrugated fins 5 of aluminum brazing sheet each disposed in
an air passage clearance between the adjacent refrigerant tubes 4
and brazed to the adjacent tubes 4, an inlet pipe 6 made of
aluminum extrudate and connected to the upper end of peripheral
wall of the first 2 of the headers, an outlet pipe 7 made of
aluminum extrudate and connected to the lower end of peripheral
wall of the second 3 of the headers, a first partition 8 provided
inside the first header 2 and positioned above the midportion
thereof, and a second partition 9 provided inside the second header
3 and positioned below the midportion thereof. The refrigerant tube
4 to be used may be an electro-resistance welded tube.
[0028] The number of refrigerant tubes 4 between the inlet pipe 6
and the first partition 8, the number of refrigerant tubes 4
between the first partition 8 and the second partition 9 and the
number of refrigerant tubes 4 between the second partition 9 and
the outlet pipe 7 decrease from above downward to provide groups of
channels. A refrigerant flowing into the inlet pipe 6 in a vapor
phase flows zigzag through units of channel groups in the condenser
before flowing out from the outlet pipe 7 in a liquid phase.
[0029] Each of the inlet pipe 6 and the outlet pipe 7 is made from
an alloy containing 0.90 to 1.50 mass % of Mn, and the balance Al
and inevitable impurities. The pipe is 30 to 43% IACS in electrical
conductivity.
[0030] The alloy for making the inlet pipe 6 and the outlet pipe 7
has an Mn content preferably of 1.0 to 1.2 mass %. The alloy for
making the inlet pipe 6 and the outlet pipe 7 is preferably 33 to
37% IACS in electrical conductivity.
[0031] When the alloy for making the inlet pipe 6 and the outlet
pipe 7 contains Cu as an inevitable impurity, the Cu content is up
to 0.05 mass %. When the alloy contains Fe as an inevitable
impurity, the Fe content is up to 0.25 mass %. When the alloy
contains Si as an inevitable impurity, the Si content is up to 0.25
mass %.
[0032] The inlet pipe 6 and the outlet pipe 7 are produced, for
example, in the following manner.
[0033] The alloy described is extruded into an inlet pipe blank and
an outlet pipe blank. These pipe blanks are held heated at 550 to
600.degree. C. in the atmosphere or in an inert gas atmosphere for
10 to 600 minutes and thereafter cooled. The rate of rise in
temperature for heating is 20 to 130.degree. C./min, and the rate
of cooling after the heating is a least 47.degree. C./min. In this
way, the inlet pipe 6 and the outlet pipe 7 are produced.
[0034] The aluminum pipe of the invention according to the above
embodiment is used as the inlet pipe and outlet pipe of the
condenser of a motor vehicle air conditioner comprising a
refrigeration cycle wherein a chlorofluorocarbon refrigerant is
used. Alternatively, the aluminum pipe may be used as the inlet
pipe and outlet pipe of the evaporator of the motor vehicle air
conditioner. Furthermore, the aluminum pipe of the invention may be
used as the inlet and outlet pipes of heat exchangers for use as
motor vehicle oil coolers, motor vehicle radiators, etc.
[0035] Additionally, the aluminum pipe of the invention is useful
for piping in motor vehicle air conditioners which have a
refrigeration cycle adapted for use with a chlorofluorocarbon
refrigerant, the refrigeration cycle comprising a compressor,
condenser and evaporator which are interconnected by piping, and
for piping in motor vehicle air conditioners which have a
refrigeration cycle adapted for use with CO.sub.2 refrigerant, the
refrigeration cycle comprising a compressor, gas cooler,
intermediate heat exchanger, expansion valve and evaporator which
are interconnected by piping.
[0036] The aluminum pipe of the invention may further be used in
motor vehicle air conditioners which have a refrigeration cycle
adapted for use with CO.sub.2 refrigerant and comprising a
compressor, gas cooler, intermediate heat exchanger, expansion
valve and evaporator, as the inlet and outlet pipes of the gas
cooler and the evaporator.
[0037] Specific examples of the invention will be described below
along with comparative examples.
EXAMPLES 1-4
[0038] Four kinds of alloys having the respective compositions
listed in Table 1 were extruded into pipe blanks 9.53 mm in outside
diameter and 1.0 mm in the wall thickness of peripheral wall.
TABLE-US-00001 TABLE 1 Max. Exam- Composition (mass %) Conductivity
corrosion ple Al Mn Cu Fe Si (IACS) depth (.mu.m) 1 Bal. 1.12 0.01
0.12 0.03 33.8 233 2 Bal. 1.09 0.01 0.15 0.05 37.0 209 3 Bal. 0.90
0.01 0.22 0.07 36.8 306 4 Bal. 1.07 0.01 0.23 0.07 40.1 494
[0039] The pipe blanks were then placed into a preheating furnace
set at an internal furnace temperature of 500.degree. C., held in
the furnace for 10 minutes, thereafter placed into a main heating
furnace set at an internal furnace temperature of 601.degree. C.
and held at a blank temperature of 600.degree. C. for 3 minutes,
whereupon the pipe blanks were cooled to a blank temperature of
570.degree. C. with nitrogen gas. The blanks were thereafter
withdrawn from the main heating furnace. The rate of rise in
temperature for heating was 30.degree. C./min, and cooling rate was
60.degree. C./min. FIG. 2 shows the heating pattern.
[0040] The pipes thus produced were checked for electrical
conductivity. Table 1 also shows the result.
[0041] The pipes were subjected to SWAAT 960 hr test and checked
for resulting corrosion. Table 1 shows the maximum depth of
resulting corrosion in the pipes. Table 2 shows the state of
corrosion in the pipes, i.e., the depth of corrosion and number of
corrosive faults. TABLE-US-00002 TABLE 2 Corrosion in the Pipes
Example 1 Example 2 Example 3 Example 4 Depth of Depth of Depth of
Depth of corrosion corrosion corrosion corrosion (.mu.m) N* (.mu.m)
N* (.mu.m) N* (.mu.m) N* Up to 100 3 Up to 100 4 Up to 100 3 Up to
100 1 100-200 3 100-200 7 100-200 10 100-200 6 200-300 1 200-300 0
200-300 2 200-300 4 300-400 0 300-400 0 300-400 1 300-400 0 400-500
0 400-500 0 400-500 0 400-500 1 N*: Number
COMPARATIVE EXAMPLES 1-4
[0042] Four kinds of alloys having the respective compositions
listed in Table 1 were extruded into pipe blanks 9.53 mm in outside
diameter and 1.0 mm in the wall thickness of peripheral wall, and
the pipe blanks were subjected to SWAAT 960 hr test without heat
treatment and checked for the resulting corrosion. The pipes were
found to have pits extending through the peripheral walls thereof
due to corrosion.
INDUSTRIAL APPLICABILITY
[0043] The aluminum pipe of the present invention is suitable as
inlet pipes and outlet pipes in heat exchanges, such as condensers
or evaporators for motor vehicle air conditioners wherein a
chlorofluorocarbon refrigerant is used, gas coolers or evaporators
for motor vehicle air conditioners wherein CO.sub.2 refrigerant is
used, motor vehicle oil coolers and motor vehicle radiators; as
pipes for the piping in motor vehicle air conditioners adapted for
use with a chlorofluorocarbon refrigerant and comprising a
compressor, condenser and evaporator which are interconnected by
piping; and as pipes for piping in motor vehicle air conditioners
adapted for use with CO.sub.2 refrigerant and comprising a
compressor, gas cooler, intermediate heat exchanger, expansion
valve and evaporator which are interconnected by the piping.
* * * * *