JPS6142773B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an aluminum alloy heat exchanger, and particularly to an aluminum alloy heat exchanger of brazing specification using a brazing sheet as the fin material. Traditionally, this type of heat exchanger uses A1100 as the tube material.
Alloy, and A3003 alloy as core material as fin material,
It is generally constructed using a brazing sheet using A4003 or 4343 alloy as the skin material. However, in such a heat exchanger, due to the influence of the fin material made of the brazing sheet, especially the Al-6~10%Si alloy skin material, in a practical environment, the tube material becomes the anode and the fin material becomes the cathode, so their relative There was a concern that corrosion of the pipe materials would be accelerated by the potential difference, and there would be a significant risk of liquid leakage reaching the through holes. The present invention aims to solve the above-mentioned drawbacks and provide an aluminum alloy heat exchanger that has even better corrosion resistance. Accordingly, the present invention provides an aluminum alloy heat exchanger in which a fin material made of a brazing sheet as described above is brazed to a tube material, wherein the tube material is
It is characterized in that it contains one or both of Si 0.5-3% and Fe 0.5-2%, and the balance is aluminum and an aluminum alloy which is an unavoidable impurity. In addition, in this specification, all percentages are by weight.
shows. Both Si and Fe are effective in enriching the natural electrode potential of the pipe material, thereby reducing the difference between the natural electrode potential of the fin material made of the brazing sheet, and preventing corrosion of the pipe material. be. If the content of Si and Fe is less than 0.5% each, the above effects cannot be sufficiently achieved to the desired extent. On the other hand, if Si exceeds 3% and Fe exceeds 2%, solid solution strengthening of the aluminum alloy increases, making it difficult to form a pipe material by extrusion or the like, which is not preferable. Therefore, most preferably
It is preferable to select a material with a content based on 2.0% Si and 1.0% Fe, and furthermore, one in which the two types of Si and Fe coexist within the range of each content mentioned above. It is most preferable to It goes without saying that the aluminum alloy described above containing Si and/or Fe has the remainder made up of aluminum and unavoidable impurities. In carrying out this invention, the fin material is the same as conventional products, with the core material being A3003 alloy and the skin material being, for example, A3003 alloy.
A brazing sheet made of A4003 alloy or A4343 alloy is used. The heat exchanger may be of any type, such as a general corrugated fin type, a cross fin type, or a drone cup type. Moreover, any method such as vacuum brazing, furnace brazing, dip brazing, etc. may be employed for brazing when assembling the heat exchanger. Examples of the present invention will be described below in comparison with conventional products. Example In view of the fact that the evaluation of the corrosion protection effect of pipe materials can be predicted based on the difference in natural electrode potential between the fin material and the pipe material, Al-1%, Fe,
Each alloy of Al-2%Si, Al-1%Si-1%Fe,
A1100 is commonly used as a pipe material for conventional products.
The natural electrode potential of the alloy, as well as the brazing sheet (core material:
A3003, skin material: A4003) skin material (Al-9%
The natural electrode potentials of the Si-based materials were measured, and the results are shown in Table 1. The electrode potential was measured using an extruded tube with a thickness of 1.0 mm as a sample of the pipe material and a rolled plate with a thickness of 1.5 mm as a sample of the fin material, and a corrosive solution of 0.5N-NaCl, pH 7, and 40℃. The electrode potential inside was measured using SCE as a reference electrode.

【table】

[Table] As is clear from the table above, in heat exchangers using conventional A1100 alloy tubing, the difference in natural electrode potential between the tubing and fin material is 0.05V, so there is a great concern about corrosion of the tubing. It is predicted that this will happen. In contrast, Al-Fe, Al-Si, shown as alloys of the present invention,
In heat exchangers using Al-Si-Fe alloy tubing, the difference in natural electrode potential between the fin material and the fin material is 0.01 to 0.02.
It is found that there is a high probability that the corrosion resistance of the pipe material will be further improved. Therefore, in order to further confirm that the heat exchanger according to the present invention actually has better corrosion resistance than conventional products, a corrugated fin type heat exchanger manufactured by vacuum brazing was subjected to salt water according to JIS Z 2371. During a spray test, A1100 was found on the pipe material.
Conventional products using alloys developed corrosion holes in the pipe material after 2000 hours, causing corrosion leakage, whereas Al-1%Si
In the product of the present invention using a pipe material made of -1% Fe alloy, no corrosion leakage was observed even after 2000 hours, and it was confirmed that the product actually has excellent corrosion resistance.

Claims (1)

[Claims] 1. In a brazed aluminum alloy heat exchanger in which a fin material made of a brazing sheet is brazed to a tube material, the tube material has Si0.5 to 3
%, Fe 0.5 to 2%, and the balance is aluminum and inevitable impurities.