JPH05105980A - Aluminum alloy for heat exchanger tube material - Google Patents

Abstract

PURPOSE:To provide an aluminum alloy for heat exchanger tube material capable of increasing the rigidity of a heat exchanger without deteriorating its productivity. CONSTITUTION:The aluminum alloy is (1) an aluminum alloy for heat exchanger tube material having a composition consisting of, by weight, 0.1-0.8% Si, 0.01-0.1% Cu, 0.2-0.8% Mg, and the balance Al with inevitable impurities and (2) an aluminum alloy for heat exchanger tube material having a composition containing, by weight, 0.1-0.8% Si, 0.01-0.1% Cu, 0.2-0.8% Mg, and further <=0.2% Cr and/or <=0.1% Ti.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy for a heat exchanger tube material used as a tube material of a heat exchanger for automobiles and the like.

[0002]

2. Description of the Related Art Generally, a heat exchanger assembled by brazing comprises tubes forming a passage for a refrigerant and cooling fins on the air side, and the fins are usually metallically joined by brazing using a brazing sheet. However, when using as a condenser or evaporator for a car cooler, use a tube (2) having a refrigerant passage in the longitudinal direction formed by hot extrusion as shown in FIG. 1, and use the tube (2) as shown in FIG. A serpentine type, as shown in Fig. 3, has been widely used in which a brazing sheet (3) that is bent in a meandering shape is attached to a tube (2) and a brazing sheet (3) formed in a corrugated shape is attached and joined by various brazing methods. It was Here, there are various tube cross-sectional shapes, but in the shape shown in FIG. 1, width 22 mm, height 5 m
m and wall thickness of 0.8 mm are used as typical dimensions.

The fin material as its constituent material is, for example, A1050 (pure Al of 99.5 wt% or more) or A30.
03 (Al-Fe-Mn system) as a core material A4004
(Al-Si-Mg system) and A4043 (Al-Si system)
It uses a brazing sheet made from. As a tube material, A1050 or A1100 (99.0 wt%
Al) has been used, but Al materials are known to have pitting corrosion due to their characteristics. Al heat exchanger tube materials have a problem of corrosion because the inner surface is in contact with an organic medium. Although it does not occur, there is a serious problem that the outer surface causes pitting corrosion when exposed to a high temperature and high humidity condition, and when it penetrates the wall thickness of the pipe material, the refrigerant sealed inside leaks. In order to overcome the problem, Al-Cu-Mn system (Japanese Patent Publication Sho 58
-56016) and Al-Cu-Ti system (Japanese Examined Patent Publication 6)
No. 0-34617) and Al—Cu—Mg system (Japanese Patent Laid-Open No. 63-262439), the corrosion resistance of the alloy itself has been improved.

However, in recent years, a technique for coating the surface of a tube material with Zn, as disclosed in Japanese Patent Laid-Open No. 58-204169, has become known, and even A1050 and A1100 have Z.
Corrosion resistance was dramatically improved by coating with n. On the other hand, the brazing method in the furnace has also been performed by the FB method using chloride-based flux and the VB method performing brazing without flux in a vacuum atmosphere, but the FB method contains Zn and Cl in the flux components. Therefore, a Zn diffusion layer is formed on the surface of the pipe during brazing,
Since this layer is lower in electric potential than Al, it acts electrochemically as a sacrificial layer and prevents through-pitting corrosion of the pipe material, but at the same time, Cl has an ionization tendency superior to Al and causes dissolution corrosion of Al members. Therefore, it is necessary to wash and remove the flux after brazing, which is troublesome and has a problem in wastewater treatment. On the other hand, the VB method does not require a flux because it is a vacuum heating, but since Zn, which has a high vapor pressure and causes evaporation loss, cannot be used, the Al base remains as it is after brazing, which makes it unusable in a harsh environment. was there. After that, a method (NB method) of brazing in a non-oxidizing atmosphere using a fluoride-based non-corrosive flux was put into practical use. This method does not require cleaning because it is non-corrosive, and the furnace pressure is almost atmospheric pressure and Zn evaporation loss is small, so its use is expanding as a brazing method that compensates for the problems of both the FB method and the VB method. is doing. The amount of the Zn-coated tube material described above is increasing as a tube material adapted to the NB method. As described above, conventional aluminum alloys for heat exchanger tubes have been improved while achieving both corrosion resistance and material productivity. Therefore, it was inevitable that the alloy composition was based on pure Al. Among the aluminum alloys, the pure Al-based alloy has excellent corrosion resistance and material productivity, but has a low strength.

In addition, recently, the flow type of the refrigerant is shown in FIG.
Unlike the serpentine type, a plurality of tubes are arranged in parallel as shown in FIG. 4, fins are arranged between adjacent tubes, and both ends of each tube are connected to a pair of aluminum aerial header tubes for communication. A heat exchanger called a parallel flow is becoming popular. This parallel flow type has excellent heat exchange performance and the core is small and lightweight. Therefore, the tube material to be used has a smaller cross-sectional shape, as shown in FIG. 5, with a width of 20 mm, a height of 2 mm, and a wall thickness of 0.4 mm as a representative dimension. However, the unit weight has been reduced to less than 1/2, but the present situation is that the tube material alloy that constitutes the core is the Al-based alloy currently used in the serpentine system. Therefore, the following problems occur.

[0006]

At present, the process of manufacturing a heat exchanger has been considerably automated from cutting of materials to processing of parts, assembling of cores, and brazing. It is important that burrs do not appear in the material when cutting and that it does not deform during transportation or assembly.Materials that are not compatible with such automated equipment are not suitable even if they have excellent brazing and corrosion resistance. I have no choice but to judge. In the conventional alloy, especially in the manufacturing process of the parallel flow heat exchanger, it may be deformed during transportation after short cutting and stuck in the middle of the line,
Even a slight deformation caused problems such as the insertion into the header tube not working properly during assembly. These are because the strength of the alloy itself is low, and the tube is small and thin so that the rigidity of the tube itself is lowered, which causes a great disadvantage to the mass productivity of the heat exchanger. Further, in the passenger car equipped with the heat exchanger according to the present invention, the weight of the vehicle body structure has been reduced in recent years, and an excessive reinforcing member tends to be omitted. Since it is regarded as a part of the vehicle body structure, the heat exchanger is also required to have rigidity against deformation and vibration, but even if the conventional alloy has low strength itself, if it is a serpentine type, the cross-sectional area of the tube is Since it is large and one tube is bent in a meandering shape, the rigidity as a heat exchanger was satisfied. However, the parallel flow type makes the heat exchanger itself lightweight and compact, and is excellent in terms of space saving and CFC saving, which are other required characteristics for in-vehicle use, but because of the small tube cross-sectional area, it has a heat exchanger structure. Has insufficient rigidity,
A disadvantage is caused by hindering the spread of the parallel flow heat exchanger having other excellent characteristics.

[0007]

In view of such a situation, the present invention improves the productivity of the heat exchanger without impairing the productivity of the raw material and the other characteristics of the heat exchanger, and at the same time, improves the productivity of the heat exchanger. An aluminum alloy for a heat exchanger tube material, which can improve the rigidity of the exchanger, has been developed. The invention according to claim 1 has Si0.1 to 0.8 wt%, Cu0.
01-0.1 wt%, Mg 0.2-0.8 wt%,
An aluminum alloy for a heat exchanger tube material, characterized in that the balance is Al and unavoidable impurities. The invention according to claim 2 has Si 0.1 to 0.8 wt% and Cu 0.0
1 to 0.1 wt%, Mg 0.2 to 0.8 wt%, further contains one or two of Cr 0.2 wt% or less and Ti 0.1 wt% or less, and the balance Al and unavoidable impurities. It is an aluminum alloy for a heat exchanger tube material, characterized in that

[0008]

The alloy of the present invention age-precipitates the intermetallic compound Mg ₂ Si by adding Si and Mg to Al to obtain the effect of improving the material strength, and at the same time, by the brazing heat of the heat exchanger assembly and the subsequent cooling. Also has the effect of precipitating Mg ₂ Si and improving the structural strength of the heat exchanger.
At the same time, by adding Cu, the potential of the alloy was increased to show excellent pitting corrosion resistance when combined with a sacrificial anode fin, and an alloy excellent in material productivity, strength, and corrosion resistance was obtained. By further adding Cr or / and Ti to this, the strength of the alloy is further improved without impairing the corrosion resistance and workability of the alloy. The reason for limiting the content of the additive element in the alloy of the present invention as described above is as follows. Mg has the effect of forming extremely fine Mg ₂ Si by the aging precipitation treatment together with Si and improving the strength. However, if the Mg content is less than 0.2%, sufficient strength cannot be obtained, and if it exceeds 0.8%, the NB brazing property deteriorates. Si dissolves in the matrix to improve the strength, and also has the effect of forming extremely fine Mg ₂ Si with Mg and improving the strength by the age precipitation treatment. However, if the Si content is less than 0.1%, sufficient strength cannot be obtained, and if it exceeds 0.8, the solidus temperature becomes low, and there is a risk of melting during the brazing heat. Cu has the effect of producing fine Al-Cu-based and Al-Cu-Mg-based precipitates, making the potential of the material noble and improving corrosion resistance. However, if the Cu content is less than 0.01%, the effect of making the potential noble cannot be obtained, and if it exceeds 0.1%, the workability is deteriorated, and the potential is increased too much, so that the self-corrosion may become remarkable. is there. When Cr and Ti exceed the upper limits, the extrudability is impaired. Especially when Cr exceeds 0.2%, coarse Al
Since the Cr compound is easily formed, the workability of the alloy is impaired, and the improvement in strength is saturated, the above limits are set.

As a method for producing a tube material from the alloy of the present invention, hot extrusion or conform extrusion can be applied. Further, as in the conventional case, by coating the tube surface with Zn, the corrosion resistance can be further improved.

[0010]

EXAMPLES The present invention will now be described in more detail with reference to examples. [Example 1] An aluminum alloy billet (diameter 175 mm) having the composition shown in Table 1 was water-cooled and the ingot was heated at 450 ° C to 4 ° C.
Extrusion die temperature of 480 after homogenization treatment at 80 ° C for 2 hours
Adjusted to ℃ ~ 510 ℃, the deformed tube shown in Fig. 4 (width 2
It was manufactured by hot extrusion into 0 mm height 2 mm wall thickness 0.4 mm) and water cooling immediately after extrusion. On the other hand, the aluminum alloy used as the fin material is Al-1.1% Mn-0.06% Mn-0.6% Z.
n as a core material, and Al-10% Si-1.5 on both surfaces
% Brazing sheet (plate thickness 0.11 mm) produced by clad rolling% Mg, and processed into a corrugated shape having a height of 10 mm and a fin pitch of 2 mm. After degreasing the above tubes and fins, restraining them with an iron jig and vacuum brazing at 600 ° C. for 3 minutes in a vacuum of 5 × 10 ^-5 Torr to equalize the cooling rate after heating, and to set the simulated core. It was made. Table 2 shows the results of various evaluations of this simulated core. First,
Extrudability is evaluated by the extrusion rate, which is a characteristic that is an index of material productivity. Here, the equivalent or higher than the conventional alloy A1050 is expressed as ◯, and inferior to A1050 is expressed as x. The material strength was indicated by the tensile strength after aging at room temperature for 4 days after extrusion. The assemblability was evaluated based on the presence or absence of bending or deformation when the simulated core was manufactured. The brazing property was evaluated by the presence or absence of a defective joint between the tube and the fin after brazing the simulated core. For the strength after brazing, the tube was taken out from the simulated core, and the tensile strength after aging at room temperature for 4 days after brazing was evaluated. The corrosion resistance was evaluated by the time until the pitting corrosion penetrated by the CASS test. Further, since the alloy of the present invention has age hardening characteristics, the strength can be further improved by performing artificial aging treatment after the heat of brazing. Here, the brazed core is heat-treated at 200 ° C for 2 hours, and the tensile strength after taking out the tube alone is shown in Table 2 as well. The rigidity of the exchanger is further improved.

[0011]

[Table 1]

[0012]

[Table 2]

As is clear from Table 2, the alloy material sample of the present invention
No. 1 to 9 are superior in strength, assemblability, core rigidity and corrosion resistance to the conventional alloy materials 16 and 17. On the other hand, the comparative alloy material sample No. 1 containing less Si and Mg than the range of the present invention. Nos. 10 and 11 have the same strength, assemblability, and core rigidity as those of the conventional alloy, and the comparative alloy material sample Nos. Having a Si content higher than the range of the present invention. No. 12 has a poor brazing property and cannot braze, and has a Mg content higher than the range of the present invention. No. 13 has poor extrudability, and contains Cr and Ti.
Comparative alloy material sample No. with a content higher than the range of the present invention 1
It can be seen that Nos. 4 and 15 have poor extrudability.

Example 2 An aluminum alloy billet (diameter 175 mm) having the composition shown in Table 1 was water-cooled and the ingot was homogenized at 450 ° C. to 480 ° C. for 2 hours, and then the extrusion die temperature was 480 ° C. to 510 °. ℃ adjustment to hot extruded into second tube (width 20mm height 2mm thickness 0.4 mm) shown in FIG. 4, the amount of deposition per unit area on the tube the entire surface immediately after extrusion 10g / m ² ~20g / m ² Zn was sprayed so that On the other hand, the aluminum alloy used as the fin material is Al-1.1% Mn-0.06% M
Using n-0.6% Zn as a core material, Al-10
A brazing sheet (sheet thickness: 0.11 mm) produced by clad and rolling% Si-1.0% Zn was processed into a corrugate shape having a height of 10 mm and a fin pitch of 2 mm.
After degreasing the above tubes and fins, they were restrained with an iron jig. Then, this is dipped in a fluoride flux bath, heated at 200 ° C. for 15 minutes and dried, and then heated at 600 ° C. for 3 minutes in a N ₂ gas atmosphere having a dew point of −40 ° C. Then, the cooling rate after heating was made equal to prepare a simulated core. Example 1 for this simulated core
Table 3 shows the results of various evaluations performed in the same manner as in.

[0015]

[Table 3]

As is clear from Table 3, the alloy material sample of the present invention
No. 21 to 29 are conventional alloy material sample Nos. It is superior in strength, assemblability, core rigidity, and corrosion resistance to 36 and 37. On the other hand, the comparative alloy material sample Nos. Containing less Si and Mg than the range of the present invention respectively. Nos. 30 and 31 have the same strength, assemblability, and core rigidity as those of the conventional alloy, and the comparative alloy material sample No. having a Si content higher than the range of the present invention. 32
Is poor in brazing property, is not brazable, and has a Mg content higher than the range of the present invention. 33 is extrudability,
Comparative alloy material sample No. 3 having poor brazing property and Cr content and Ti content exceeding the respective ranges of the present invention. It can be seen that 34 and 35 have poor extrudability.

Example 3 An aluminum alloy wire having the composition shown in Table 1 was prepared, and the extrusion die temperature was adjusted to 480 ° C. to 510 ° C. by a conform extruder, and the deformed tube shown in FIG. 2 mm thick and 0.4 mm thick) was continuously pipe-formed, and water-cooled immediately after extrusion to manufacture. On the other hand, the aluminum alloy used as the fin material is Al-1.1% Mn-0.06%
Mn-0.6% Zn was used as the core material, and Al-1
A brazing sheet (sheet thickness 0.11 mm) produced by clad rolling 0% Si-1.5% Mg, which has a height of 1
It was processed into a corrugated shape with 0 mm and fin pitch of 2 mm. After degreasing the above tubes and fins, restrain them with an iron jig.
Vacuum brazing was performed at 600 ° C. for 3 minutes in a vacuum of × 10 ^-5 Torr to make the cooling rate after heating equal, and a simulated core was produced. Table 4 shows the results of various evaluations performed on this simulated core in the same manner as in Example 1. Here, the material strength is higher in the conform extrusion, but this is because the heating time is shorter than in the hot extrusion and the material is rapidly cooled.

[0018]

[Table 4]

As is clear from Table 4, the alloy material sample of the present invention
No. 41 to 49 are superior in strength, assemblability, core rigidity and corrosion resistance to the conventional alloy materials 56 and 57. On the other hand, the comparative alloy material sample No. 1 containing less Si and Mg than the range of the present invention. Nos. 50 and 51 have the same strength, assemblability, and core rigidity as the conventional alloy material, and the comparative alloy material sample No. having a Si content higher than the range of the present invention. No. 52 has a poor brazing property and cannot braze, and has a Mg content higher than the range of the present invention. 53 has poor extrudability and is Cr
Comparative alloy material sample No. 1 whose content and Ti content are higher than the range of the present invention. It can be seen that 54 and 55 have poor extrudability.

Example 4 An aluminum alloy element wire having the composition shown in Table 1 was prepared, and the extrusion die temperature was adjusted to 480 ° C. to 510 ° C. by a conform extruder and the deformed tube shown in FIG. is continuously forming tube to 2mm thickness 0.4 mm), coating weight per unit area on the tube the entire surface immediately after extrusion is sprayed Zn so as to be ^{10g / m 2 ~20g / m 2} , and water-cooled immediately thereafter Manufactured. On the other hand, the aluminum alloy used as the fin material is Al-1.1% Mn-0.06% M
Using n-0.6% Zn as a core material, Al-10
% Si-1.0% Zn is a brazing sheet (plate thickness 0.11 mm) produced by clad rolling.
mm, fin pitch 2 mm processed into a corrugated shape. After degreasing the above tubes and fins, they were restrained with an iron jig. Then, after immersing it in a fluoride-based flux bath, 2
Dried point of -40 after heating and drying at 00 ℃ for 15 minutes
By brazing by heating at 600 ° C. for 3 minutes in a N ₂ gas atmosphere at 0 ° C., the cooling rate after heating was made equal, and a simulated core was produced. Table 5 shows the results of various evaluations performed on this simulated core in the same manner as in Example 1.

[0021]

[Table 5]

As is clear from Table 5, the alloy material sample of the present invention
No. 61 to 69 are superior in strength, assemblability, core rigidity and corrosion resistance to the conventional alloy materials 76 and 77. On the other hand, the comparative alloy material sample Nos. Containing less Si and Mg than the range of the present invention respectively. Nos. 70 and 71 have the same strength, assemblability, and core rigidity as those of the conventional alloy material, and the comparative alloy material sample No. having a Si content higher than the range of the present invention. 72
Is poor in brazing property, is not brazable, and has a Mg content higher than the range of the present invention. 73 is extrudability,
Comparative alloy material sample No. 3 having poor brazing property and Cr content and Ti content exceeding the respective ranges of the present invention. It can be seen that 74 has poor extrudability.

[0023]

As described above, the alloy material of the present invention improves the assembling property and rigidity of the heat exchanger by improving the material strength and the strength after brazing, and the parallel flow type heat exchange which is expected to grow in demand in the future. This has a remarkable effect on the improvement of mass productivity and expansion of applications.

[Brief description of drawings]

FIG. 1 is a perspective view showing an example of a heat exchanger tube.

FIG. 2 is a perspective view showing a portion of a serpentine heat exchanger.

FIG. 3 is a front view showing an example of a serpentine heat exchanger.

FIG. 4 is a front view showing an example of a parallel flow heat exchanger.

FIG. 5 is a perspective view showing an example of a tube of a parallel flow heat exchanger.

[Explanation of reference numerals] 1 tube (folded portion) 1a refrigerant passage 2 tube (flat portion) 3 fins 4 refrigerant inlet / outlet fitting 5 hollow header tube

Claims (2)

[Claims] 1. Si 0.1-0.8 wt%, Cu 0.01
An aluminum alloy for a heat exchanger tube material containing 0.1 to 0.1 wt% and Mg 0.2 to 0.8 wt% and the balance Al and inevitable impurities. 2. Si 0.1 to 0.8 wt%, Cu 0.01
.About.0.1 wt%, Mg 0.2 to 0.8 wt%, and one of Cr 0.2 wt% or less and Ti 0.1 wt% or less.
An aluminum alloy for a heat exchanger tube material, which contains one or two kinds and comprises the balance Al and unavoidable impurities.