JPH0320435A - Aluminum alloy for heat exchanger - Google Patents

Abstract

PURPOSE:To obtain the Al alloy for a heat exchanger having excellent strength after brazing while retaining excellent corrosion resistance and workability by specifying the compsn. constituted of Mg, Si, Mn, Fe, Cu and Al. CONSTITUTION:The Al alloy for a heat exchanger contains, by weight, 0.1 to 0.8% Mg, 0.3 to 1.0% Si, 0.3 to 1.5% Mn and 0.01 to 0.3% Fe, furthermore contains, at need, one or both of 0.05 to 0.3% Cr and 0.01 to 0.05% Ti, in which Cu as impurities is regulated to <=0.05% and the balance Al with other inevi table impurities, which retains corrosion resistance and workability equal to or above those of an A3003 alloy and has increased strength after brazing. Thus, a lightweight heat exchanger having prolonged service life in which tubes, substructural members, etc., have improvement in thinning, lightening in weight and durability can be obtd. at low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to an aluminum alloy for heat exchangers used for tubes and sub-components such as header plates, side plates, etc. of various heat exchangers such as radiators, car heaters, and intercoolers. .

Conventional technology Conventionally, in the above-mentioned heat exchangers, A3003 alloy, which has relatively excellent corrosion resistance and workability, has been generally used as a material for the tubes through which the heat exchange medium flows and the heat exchanger sub-structural members. Ta.

Problem to be Solved by the Invention However, in the case of the A3003 alloy, when brazing is performed to join each component in the production of a heat exchanger, the strength after brazing is low (yield strength σa.t*4Kyf
/mA). For this reason, in order to ensure sufficient strength for tubes, etc., the wall thickness must be increased.
As a result, they had no choice but to accept an increase in the size, weight, and cost of the heat exchanger.

This invention was made in view of such circumstances, and
The purpose of the present invention is to provide an aluminum alloy for heat exchangers that can be used as tubes, sub-components, etc., and has improved strength after brazing while maintaining corrosion resistance and workability equivalent to or higher than A3003 alloy.

Means for Solving the Problems The above purpose is as follows: Mg: 0. 1~0. 8wt%,
Si: 0. 3 ~1.・Owt%, Mn:
0. 3 to 1.5 wt%, Fe: 0.01 to O. 3
wt% or roughly Cr: 0. 0
5 ~ 0. 3wt%, Ti: 0, 01~0.05wt
% of IN or two kinds, and Cu: 0.0% as an impurity.
The aluminum alloy for heat exchanger tubes is characterized by being regulated to 0.5 wt% or less, with the remainder consisting of aluminum and other unavoidable impurities.

First, to explain the significance of adding each element and the reason for limiting the composition range, Mg contributes to improving the strength after brazing, but if it is less than 0.1 wt%, the above effect is poor; If the content exceeds 8 wt%, brazing failure will occur. A particularly preferable Mg content range is 0.2 to 0.
It is 5wt%.

St also contributes to improving the strength after brazing, but 0. If the content is less than 3 wt%, the above effects will be poor, and if the content exceeds 1.0 wt%, brazing defects will still occur. A particularly preferable Si content range is 0. 6w
It is more than t% and less than 0.9wt%.

Mn is effective in improving corrosion resistance and strength. But 0. If it is less than 3 wt%, the above effect will be poor, and conversely, if it is less than 1
．． If it exceeds 5 wt%, the effect will be saturated and not only will it not be possible to obtain an effect commensurate with the increase in cost, but it will also produce bulky products and deteriorate processability. A particularly preferable Mn content range is 0
. It is 5 to 1.2 wt%.

Fe contributes to grain refinement, strength improvement, and suppression of intergranular corrosion at high temperatures, but if it is less than 0.01 wt%, it has no effect. If it exceeds 3 wt%, the effect will be saturated. A particularly preferable Fe content range is 0.02 to 0.
It is 2wt%.

In addition to the above-mentioned essential elements, Cr contributes to suppressing intergranular corrosion among C' and Ti, which may be optionally included in one or two kinds. However, if it is less than 0.05 wt%, the effect is poor; If it exceeds 3 wt%, the effect will be saturated. The particularly preferable content range of C' is 0.06 to 0.
．． It is 2wt%. Furthermore, although Ti exhibits a crystal grain refining effect, if it is less than 0.01 wt%, the effect is poor;
If it exceeds 0.05 wt%, the effect will be saturated.

A particularly preferable Ti content range is 0.02 to 0.04wt
%.

Further, among impurities that are inevitably included, Cu deteriorates corrosion resistance, so its content must be regulated to 0.05 wt% or less.

When manufacturing the aluminum alloy according to the present invention into, for example, a tube material, it may be extruded into a tube material by a conventional extrusion method, or it may be extruded and then pulled out.
Or after rolling it into a plate material by a conventional rolling method,
It may be made into a pipe material by electric resistance welding, and the manufacturing method thereof is not limited. Further, as shown in Fig. 1, the tube (1) may be made of the above-mentioned aluminum alloy alone, or as shown in Fig. 2, the aluminum alloy may be used as the core material (2) to form the outer surface for joining with the fins. A brazing material layer (3) made of AQ-Si alloy or the like is covered with a cladding or the like to form a tube (
1') may also be used. In addition, especially when highly corrosive water or the like is used as a heat exchange medium, such as in a heat exchanger for overnight radio work, in order to give the tube even better corrosion resistance, it is necessary to Alternatively, the inner surface may be coated with a sacrificial anode layer (4) made of A7072 alloy or the like. On the other hand, when manufacturing heat exchanger sub-components such as header plates and side plates, extrusion may be used as well, or rolling may be performed using a conventional rolling method. Further, as shown in FIG. 3, the sub-component member (5) may be made of the above-mentioned aluminum alloy alone, but as shown in FIG. It is common to coat the layer (7) as a sub-component (5'). Note that natural aging after brazing may be used to further improve the strength of the tube and sub-components.

Effects of the Invention The aluminum alloy for heat exchangers according to the present invention has corrosion resistance and processing properties equivalent to or higher than that of the conventional A3003 alloy, as will be clear from the examples described below, due to the combination of specific elements and their composition ranges. It is possible to increase the strength after brazing even though it has properties. Therefore,
It is possible to reduce the thickness and weight of tubes, sub-components, etc., and improve durability, thereby making it possible to provide a lightweight, long-life, and inexpensive heat exchanger.

Example Next, examples of this invention will be shown.

[Left below] Aluminum alloys with various compositions shown in Table 1 above are melted,
After casting and then homogenizing, hot rolling at 500°C, intermediate annealing at 370°C for 2 hours, cold rolling at 600°C.
A final heat treatment of 5 minutes was sequentially performed to obtain a thickness of 1. Or
A specimen for an MR heat exchanger was manufactured. It should be noted that, with the exception of No. 2, processing could be carried out without any problems, whereas in the case of alloy No. 10, which has an excessive Mn content, the diameter of 10
A Fe--Mn based intermetallic compound having a diameter of 0 μm or more was formed, and the workability was poor.

Next, the various test pieces obtained above were subjected to a brazing test.
Two types of corrosion resistance tests in different corrosive environments were conducted under the following conditions.

■Brazing test Each specimen is 50M wide x 50m long, and A300
A mating material with a width of 50a*×length of 50ma+ was prepared, which was a core material clad with BA4045 brazing filler metal on both sides. Then, as shown in Figure 5, the test piece (8) and the mating material (9) were combined in a T-shape, and brazed at 600°C for 5 minutes using fluoride flux in an N2 gas atmosphere. The fillet shape and condition of the joint after brazing were visually observed, and the yield strength of the specimen was measured.

■ Corrosion resistance test (1) This test is a test that takes into account the internal environment especially when used as a tube material.
After immersion in the u solution at 95°C for 500 hours, the depth of pitting corrosion was measured.

■Corrosion resistance test (2) This test is a test that takes into account the external environment of tubes and sub-structures or members, and each specimen is
After carrying out a salt water spray test according to JIS Z2371 for 1000 hours, the corrosion state was examined.

The above test results are shown in Table 2.

[Blank below] From the results in Table 2 above, it can be seen that the aluminum alloys according to the present invention (Nos. 1 to 8) are A3003 alloy (No. 4).
), it has excellent strength after brazing, and there are no problems with brazing properties. On the other hand, No. 9 and No. 10, which have excessive contents of Mg and S1, have poor brazing properties, and No. 1, which has a low Mn content and a large amount of Cu as an impurity, has poor corrosion resistance, and has a high content of Mg SS i. Less Nol
No. 3 and No. 4, which is an A3003 alloy, had poor strength.

[Brief explanation of drawings]

Fig. 1 is a sectional view showing an example of a heat exchanger tube using the aluminum alloy of this invention, Fig. 2 is a sectional view showing a modified example of the tube, and Fig. 3 is a sectional view showing an example of a heat exchanger tube using the aluminum alloy of this invention. FIG. 4 is a sectional view showing an example of an exchanger sub-component, FIG. 4 is a sectional view showing a modification of the sub-component, and FIG. be. (1) (1')...Tube, (2)...Heartwood, (
3)...brazing metal layer, (4)...sacrificial anode layer, (5)
(5')... Sub-component member, (6)... Core material, (7)
...Brazing metal layer. that's all

Claims (2)

[Claims] (1) Mg: 0.1-0.8wt%, Si: 0.3-1
．． 0 wt%, Mn: 0.3 to 1.5 wt%, Fe: 0.
Cu: 0.01 to 0.3 wt% as an impurity.
1. An aluminum alloy for heat exchangers, characterized in that the content is regulated to 0.5 wt% or less, and the remainder consists of aluminum and other unavoidable impurities. (2) Mg: 0.1-0.8wt%, Si: 0.3-1
．． 0 wt%, Mn: 0.3 to 1.5 wt%, Fe: 0.
01 to 0.3 wt%, and further contains Cr: 0.05 to 0.05 wt%.
0.3 wt%, Ti: 0.01 to 0.05 wt%, and Cu: 0.05 wt% as an impurity.
% or less, and the remainder consists of aluminum and other unavoidable impurities.