JPH04198694A - Heat exchanger having good anticorrosion and heat transfer property - Google Patents

Abstract

PURPOSE:To obtain a heat exchanger prominent in anticorrosion and heat transfer property by a method wherein a fin member is constituted of the core material of an aluminum alloy having a specified composition and brazing sheets on both surfaces of the core material while the fin is brazed to an operating fluid passage constituted of an extruded tube of aluminum having a specified purity. CONSTITUTION:A fin member 1 is constituted of the core material of aluminum alloy, containing Fe: 0.8-1.8% (weight % and the same hereinafter), Zn: 0.3-3.0%, Cu: 0.3% or less, one or two kinds of Zr: 0.05-0.25% and Cr: 0.05-0.25%, impurity or Mn: 0.3% or less and the remaining aluminum and the other inevitable impurities, and brazing sheets, applied on both surfaces of the core member as the skin material of Al-Si brazing material. An operating fluid passage is constituted of an extruded tube 2 consisting of the aluminum alloy of purity 99% or more of aluminum while the fin member 1 is brazed to the operating fluid passage. A heat exchanger, prominent in anticorrosion and heat transfer property, can be obtained in such a manner whereby the improvement of reliability, miniaturization and the reduction of weight of the heat exchanger can be achieved.

Description

[Detailed Description of the Invention] [Industrial Application Fields] The present invention is applicable to car air conditioner condensers, evaporators,
The present invention also relates to an Al heat exchanger such as a radiator, intercooler, oil cooler, etc. in which fins and working fluid passage constituent materials are joined by brazing, and particularly to a heat exchanger with excellent corrosion resistance and heat conductivity.

[Prior Art] In car air conditioner condensers and evaporators, or heat exchangers such as radiators, heaters, intercoolers, and oil coolers, aluminum alloy working fluid passage constituent material and aluminum alloy fin material are assembled by brazing. It is being The brazing filler metal may be placed on the channel forming material side or on the fin material side. In the latter case, an extruded tube is used as the passage construction material, and the core material of the fin material is aluminum alloy, and A is coated on both sides of the tube.
A composite material clad with l-8t alloy brazing filler metal is used.

For extruded tubes, use pure aluminum such as 1050.1070.1100 or Cu up to about 0.5%.
An aluminum alloy containing Mn or Mn is used. and,
Fin materials are required to have a sacrificial anode effect to protect extruded tubes from corrosion, and brazing requires excellent high-temperature buckling resistance to prevent deformation or corrosion due to high-temperature heating. Ru. In brazing, addition of Mn is effective in preventing deformation over time and erosion of the solder, and Al-Mn alloys such as 3003 alloy and 3203 alloy are used as the core material.

In order to impart a sacrificial anode effect, a method has been proposed in which Zn, Sn, In, etc. are added to the Al-catalytic alloy to make it electrochemically less noble (see, for example, Japanese Patent Publication No. 5B-12395). There is. A heat exchanger combining an extruded tube and fin material as described above was developed, for example, in the
9-52780.

In addition, the present applicants have discovered that without first incorporating Mn,
We have proposed a heat exchanger fin material (Japanese Patent Application No. 1-218648) that has excellent strength and thermal conductivity by containing an increased amount of Pe.

[Problems to be Solved by the Invention] By the way, as mentioned above, when a pure aluminum extruded tube is combined with a fin material made of an Al-Mn alloy with Zn, Sn, In, etc. added, a certain degree of anti-corrosion effect can be expected. However, because the potential of the tube and the fins are close, the corrosion protection distance (the distance reached by the sacrificial anode effect) is short, and there is a problem that pitting corrosion is likely to occur in the portion of the tube away from the fins. If an extruded tube made of an alloy containing Cu or Mn is used instead of an extruded tube made of pure aluminum, the electric potential of the tube becomes a liability and the potential difference between the tube and the fin increases, and the corrosion protection distance tends to become longer. However, Cu and M
If n is increased, the extrudability of the tube (multi-hole tube) becomes poor, so the amount of Cu or Mn added is limited to about 0.5%, and for this reason, no fundamental solution has been reached.

In addition, recently, zinc-coated tubes have been increasingly used as passage construction materials, and in this case, a zinc diffusion layer is formed during brazing to protect the tubes from corrosion. Then, such a tube and a conventional fin material, that is, Al-
When using a fin material made by adding Zn-5ns1n to Mn, the potential of the zinc diffusion layer is less noble than that of the fins, so the zinc diffusion layer corrodes earlier than the fins, causing corrosion to occur from the tube. There is a problem with the fins coming off.

Furthermore, in recent years, there has been a strong demand for lighter weight and lower cost heat exchangers, and in order to meet these demands, it is necessary to make the constituent materials of heat exchangers (working fluid passage constituent materials, fin materials, etc.) thinner. It has become necessary. However, when the fin material is made thinner, the heat transfer cross-sectional area becomes smaller, which poses a problem in that heat exchange performance is impaired.

In order to solve this problem, it is effective to increase the thermal conductivity of the fin material after brazing, but in the case of the core material of ^l-Mn alloy, brazing is sometimes performed at high temperatures and the Mn becomes hard. Because it dissolves, the thermal conductivity decreases significantly. In addition, attempts have been made to use fin materials made by adding Zn, Sn, In, Cr5Ti, Zr, etc. to pure aluminum (1050, 1070, etc.) in order to increase thermal conductivity, but in this case, high temperature resistance It has poor buckling properties, and although it has high thermal conductivity, the strength after brazing is low and the fins tend to collapse, so this has not fundamentally solved the problem.

The previously proposed ``heat exchanger fin material that does not contain Mn (increased amount of Pe) provides excellent strength and thermal conductivity'' does not have Al-8t brazing filler metal on both sides of the core material. Therefore, it is not suitable for making heat exchangers in combination with extruded tubes.

The present invention aims to fundamentally solve these problems.

[Means for Solving the Problems] The present inventors have studied various aluminum alloys, and found that the thermal conductivity after brazing is lower than that of conventional fin materials whose core material is Al-Mn alloy. We have discovered a brazing fin material that has significantly improved strength, sacrificial anode effect, and high-temperature buckling resistance, and we have developed this fin material and an extruded tube of pure aluminum or an alloy containing CuS Mn, or these extruded tubes. It was discovered that a heat exchanger with excellent corrosion resistance and heat conductivity can be produced by combining a heat exchanger with an extruded tube whose surface is coated with zinc, and the present invention has been completed.

That is, the present invention is as follows.

(1) Fe: 0.8-1.8%, Zn: OJ
~3.0%, Cu: 0.3% or less, and further Z
r: 0.05-0.25%, Cr: 0.05-0.
Contains 25% of one or two types of Mn as an impurity.
The core material is an aluminum alloy consisting of 0.3% or less and the balance is Al and other unavoidable impurities.
The fin material is composed of a brazing sheet made of l-8i brazing material as a skin material, the working fluid passage is composed of an extruded tube made of an aluminum alloy with an Al purity of 99% or more, and the fin is brazed to the working fluid passage. A heat exchanger with excellent corrosion resistance and heat transfer properties.

(2) Fe: 0.8~IJ%, Zn: 0.3~
3.0%, Cu: 0.3% or less, and Zr:
0.05-0.25%.

Cr: Contains one or two of 0.05 to 0.25%, Mn as an impurity is 0.3% or less, and the balance is A.
A fin material is constituted by a brazing sheet made of an aluminum alloy consisting of l and other unavoidable impurities as a core material, and a brazing sheet made of an Al-8i brazing material as a skin material on both sides,
A working fluid passage is constituted by an extruded tube made of an aluminum alloy containing one or two of Cu: 0.5% or less and Mn - 0.5% or less, and the remainder being Al and unavoidable impurities. A heat exchanger with excellent corrosion resistance and heat conductivity, characterized by having fins brazed to the passages.

(3) The extruded tube made of aluminum alloy constituting the working fluid passage has a Zn coating layer of 1 to 25 g/m2 on the surface thereof, which has excellent corrosion resistance and heat conductivity. exchanger.

(4) The extruded tube made of aluminum alloy constituting the working fluid passage has a Zn coating layer of 1 to 25 g/m2 on the surface thereof, which has excellent corrosion resistance and heat conductivity. exchanger.

The reasons for limiting each composition in the present invention are as follows.

(1) Fin material (a) Core material Fe: re is the strength of the alloy, that is, brazing improves the strength of the previous fin material as well as the strength after brazing.

Since the alloy of the present invention does not contain Mn, 0.8% or more of Fe is required to improve the strength. The more Pe there is, the higher the strength is, and 1.0% or more is desirable. On the other hand, 1.8%
If this value is exceeded, coarse crystallized substances will be generated during casting, making it difficult to manufacture plate materials.

Unlike iron, Pe does not become solid solution during soldering and does not reduce thermal conductivity or affect potential, so it is a fin material with excellent thermal conductivity and sacrificial anode effect, especially sacrificial anode effect for zinc-coated tubes. Suitable as an additive element to the core material.

Zn: Zn makes the potential of the fin material less noble and provides a sacrificial anode effect. In particular, when Zn is added to an Al-Pe alloy, the potential effectively becomes less noble, and when used in combination with a bare tube, the corrosion protection distance (reaching distance of the sacrificial anode effect) becomes longer.
In addition, in combination with a zinc-coated tube, the sacrificial anode effect on the zinc diffusion layer becomes better. If it is less than the lower limit, the effect will not be sufficient, and if it exceeds the upper limit, the self-corrosion resistance will deteriorate.

Cu: Cu improves strength after brazing. If the upper limit is exceeded, the potential of the fin material becomes a liability and the sacrificial anode effect is impaired.

Zr, Cr: Zr and Cr improve high temperature buckling resistance. If it is less than the lower limit, the effect will not be sufficient, and if it exceeds the upper limit, the thermal conductivity after brazing will decrease.

Mn: Hnti as an impurity. As mentioned above, if the content increases, the thermal conductivity will decrease and the electric potential will be affected, so it is preferable to have a small amount.

However, its content is permissible as long as it is 0.3% or less.

Other elements may include St, Mg, Ti, etc. within a range that does not impair the effects of the alloy of the present invention. however,
In either case, as the content increases, the thermal conductivity decreases. Therefore, Si is 0.6% or less, Mg is 0.2% or less, and Tj is 0.
,05% or less. Since Mg reacts with the flux when fluoride flux brazing is performed, it is desirable to keep it even lower, that is, to 0.1% or less. Ti may be added as an alloying element for grain refinement during casting, or as a ^1-Ti-B refiner, but it is desirable to suppress it within the above range.

(b) Brazing filler metal An Al-St alloy is used as the brazing material.

Usually, an alloy containing 6 to 13% of St is used. A part of the Si in the brazing filler metal diffuses into the core material (solid diffusion) and contributes to improving the strength.

Furthermore, Zn may be added to the brazing material in order to enhance the sacrificial anode effect of the entire fin material.

(2) Tube material The tube material should be pure aluminum with an Al purity of 99% or more, or CuO, 5% or less, and MnO, 5%.
An aluminum alloy containing one or two of the following, with the balance being Al and unavoidable impurities is used. In the former case, if the Al purity is less than 99%, corrosion resistance will deteriorate, which is not preferable. Usually industrial pure aluminum 1050.
1070S1100 or the like is used. On the other hand, in the latter case, Cu and Mn are added in order to increase the potential difference between the tube material and the fin material, thereby increasing the anticorrosion effect due to the sacrificial anode effect of the fin material. This effect is due to Cu
The higher the amount of Cu and the amount of Mn, the higher the amount, but on the other hand, if the amount of Cu and the amount of Mn each exceed 0.5%, the extrudability of the tube (extruded multi-hole tube) decreases.

When these tubes (bare tubes) are combined with the fin material of the above (present invention), a heat exchanger with a long corrosion protection distance and excellent corrosion resistance can be obtained. Of course, it also has excellent heat conductivity.

Further, a tube in which the surface of the above-mentioned tube material is coated with zinc may also be used. In this case, a zinc diffusion layer is formed during soldering and the tube is protected from corrosion. The amount of zinc to be coated is preferably in the range of 1 to 25 g/m'. If it is less than Ig/a', the anticorrosion effect will be insufficient, and if it exceeds 25 g/l112, the surface zinc concentration after diffusion will increase, the zinc diffusion layer will corrode quickly, and the fins will separate from the tube.

Methods of coating zinc on the surface of the tube include thermal spraying,
There are such things as Metsuki.

When such a zinc-coated tube is combined with the fin material of the present invention, a heat exchanger with good corrosion resistance and fins that are less likely to come off can be obtained. Of course, it also has excellent heat conductivity.

[Example 1] A-P core material alloy shown in Table 1 and brazing material alloy 43
43 (Al-7, 5% Si) was melted and cast. Homogenize the ingot of the alloy for the core, combine it with a filler metal that has been hot rolled in advance, and perform hot rolling, cold rolling, intermediate annealing and final cold rolling. 0.121
Brazing fin materials Nos. 1 to 16 (brazing fin materials No. 1 to 16 with a brazing metal cladding ratio of 10% on both sides) were produced. Next, brazing was performed by heating in nitrogen gas for 3 minutes at 600°C, followed by a tensile test and electrical conductivity measurement, and the pH was adjusted to 3%.
After immersion in the NaCl aqueous solution for 8 hours, the natural electrode potential was measured. Note that since the thermal conductivity and electrical conductivity of metals are generally in a proportional relationship, here, the electrical conductivity (at 25° C.) was measured instead of the thermal conductivity. Also, 60
After heating at 0° C. for 3 minutes, the state of corrosion of the wax into the core material was observed by cross-sectional metallographic structure, and brazeability was determined.

The above results are shown in Table 2.

In the case of the present invention examples No. 1 to 5, the tensile strength and electrical conductivity after brazing are high, the brazing property is better than the conventional fin material No. 1B, and the natural electrode potential is also base and sacrificial. Excellent anode effect.

Comparative Example No. 6 has a low tensile strength due to a small amount of Fe in the core material, whereas Comparative Example No. 7 has a large amount of Fe, so a sound fin material cannot be obtained.

No. 8 has a small amount of Zn in the core material, so the natural electrode potential is somewhat at fault. Since N009 contains a large amount of Zn, its electrical conductivity is somewhat low.

No. 10 has a slightly low tensile strength because the core material does not contain Cu.

No. 11 has a high natural electrode potential due to the large amount of Cu in the core material.

No. 12 has poor brazing properties because the core material contains less Zr and Cr. No. 13 and No. 14 have low electrical conductivity because they contain a large amount of Zr or Cr.

No. 15 had low electrical conductivity due to the large amount of Mn in the core material, and the natural electrode potential was somewhat at fault.

No. 1I3 is a conventional fin material with a core material of 3003+Zn alloy, but its tensile strength is somewhat low, its electrical conductivity is low, and its natural electrode potential is somewhat noble.

Table 1 *Table 2 Example 2 of 3003 with Zn added The fin material prepared in Example 1 was corkated and
A test piece as shown in FIG. 1 was prepared by combining the extruded tubes a to d in the table (without zinc coating) and brazing with fluoride flux. This test piece was used for 4 weeks of 5IdAAT test (A
STM G43), and the maximum corrosion depth of the tube at the fin joint, the corrosion protection distance (the shortest distance from the point where deep pitting corrosion occurred in the non-fin joint to the fin joint), and the corrosion status of the fin were investigated.

The results are shown in Table 4.

In the case of invention examples No. 17 to 27, the maximum corrosion depth is small, the corrosion protection distance is large, and the corrosion state of the fins is normal.

In the case of Comparative Example No. 28, the maximum corrosion depth was large and the corrosion protection distance was short because the fin core material contained less Zn. No, 2
In the case of No. 9, there is a large amount of Zn in the fin core material, so the wear of the fins is significant. In the case of No, 30, Cu in the fin core material
Because of the large amount of corrosion, the maximum corrosion depth is large and the corrosion protection distance is short.

In the case of No. 31, the corrosion protection distance is short because of the large amount of Mn.

In the case of No. 32, the corrosion protection distance is short because the fin core material is 3DO3+Zn.

Table 3 Table 4 Example 3 The fin material produced in Example 1 was corrugated and the third
A serpentine type capacitor as shown in Fig. 2 was made by combining with the zinc sprayed tube shown in the table eh and fluoride flux brazing.

This capacitor was tested by CASS test (JISD02) for 4 weeks.
01) and 4-week salt spray test (JIS Z 23
71) i: #l, The maximum corrosion depth of the tube, the corrosion test status of the fin, and the status of separation of the fin from the tube were investigated.

The results are shown in Table 5.

In the case of Invention Examples No. 33 to 40, the maximum corrosion depth was small, the corrosion state of the fins was normal, and the fins did not come off.

In the case of Comparative Examples No. 41 to 45, the maximum corrosion depth is small because the tubes are zinc sprayed tubes, but No.
In 4L No. 43, No. 44, No. 45, the fins were detached, and in No. 42, the fins were noticeably worn out.

Table 5 Example 4 The fin material produced in Example 1 was corrugated and the third
A parallel flow type capacitor as shown in FIG. 3 was manufactured by combining the extruded tubes b and h in the table. This capacitor was installed in an air conditioner system and the amount of heat exchange was measured.

The results are shown in Table 6.

In the case of Inventive Examples No. 46 to 50, the amount of heat exchange is increased compared to Comparative Example No. 54, which is a conventional combination.

In the case of Comparative Example No. 51, 52, and 53, the heat exchange amount is about the same as No. 54 because the thermal conductivity of the fin material is low.

Based on the heat exchange amount of Comparative Example No. 54 in Table 6, the increase from that amount is expressed as a percentage.

[Effects of the Invention] According to the present invention, a heat exchanger with excellent corrosion resistance and heat conductivity can be provided, contributing to improved reliability, size reduction, and weight reduction of the heat exchanger.

[Brief explanation of the drawing]

FIG. 1(a) is a front view showing an example of a test piece for testing the effects of the present invention, FIG. 1(b) is an end view of the same, and FIG. 2 is a front view of a serpentine capacitor also used in the test. Third
The figure is a front view of a parallel flow capacitor also used in the test. l...Fin, 2...Tube, 3...Header. Patent applicant: Sumitomo Light Metal Industries, Ltd.

Claims (4)

[Claims] (1) Fe: 0.8 to 1.8% (weight%, same below),
Contains Zn: 0.3 to 3.0%, Cu: 0.3% or less, and further contains Zr: 0.05 to 0.25%, Cr: 0.05 to
The core material is an aluminum alloy containing 0.25% of one or two kinds of Mn as an impurity, 0.3% or less of Mn as an impurity, and the balance being Al and other unavoidable impurities, and an Al-Si based wax is applied on both sides of the aluminum alloy. The fin material is composed of a brazing sheet made of aluminum alloy as a skin material, the working fluid passage is composed of an extruded tube made of an aluminum alloy with an Al purity of 99% or more, and the fin is brazed to the working fluid passage. A heat exchanger with excellent corrosion resistance and heat transfer properties. (2) Fe: 0.8-1.8%, Zn: 0.3-3.0
%, Cu: 0.3% or less, and Zr: 0.05
~0.25%, Cr: 0.05~0.25% or two, Mn as an impurity is 0.3% or less, and the balance is Al and other unavoidable impurities. The fin material is composed of a brazing sheet made of a core material and an Al-Si brazing material as a skin material on both sides, and contains one or two of Cu: 0.5% or less and Mn: 0.5% or less. A heat exchanger with excellent corrosion resistance and heat conductivity, characterized in that a working fluid passage is constituted by an extruded tube made of an aluminum alloy with the remainder being Al and unavoidable impurities, and fins are brazed to the working fluid passage. vessel. (3) 1 to 25 g/m^2 of Zn is added to the surface of the extruded tube made of aluminum alloy constituting the working fluid passage.
A heat exchanger with excellent corrosion resistance and heat conductivity according to claim 1, characterized in that it has a coating layer. (4) 1 to 25 g/m^2 of Zn is added to the surface of the extruded tube made of aluminum alloy constituting the working fluid passage.
A heat exchanger with excellent corrosion resistance and heat conductivity according to claim 2, characterized in that it has a coating layer.