JPS6013057B2 - Aluminum alloy material for heat exchangers with anti-corrosion properties - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an aluminum alloy material for heat exchangers having anti-corrosion properties, which has a crystal grain size of 500 F or more after a heat recrystallization treatment following cold stretching. The aim is to impart anti-corrosion properties to aluminum alloy materials.

Traditionally, aluminum alloys were generally made to have their grain size as fine as possible to improve their strength, and depending on the application, they were treated with coatings, chemical conversion coatings, metal spraying, plating, or metal diffusion coatings to provide anti-corrosion properties. However, there are many metallographic defects such as dislocations and segregation in the grain boundaries of the structure with fine grain size, and as a result, the grain boundaries are easily corroded. Pitting corrosion occurs from that part.

Furthermore, the various treatments described above to impart corrosion resistance have not yet been able to completely prevent pitting corrosion in aluminum alloy materials for heat exchangers.

The present invention contains Mg0.2-2.0%, Feo. 1-1.0%
, Cuo. 05-0.4%, Mno. An aluminum alloy containing one or more of 3 to 2.0% of the above crystals by increasing the crystal grain size to 500 μm or more after the heat recrystallization treatment following the cold stretching process. Reduces grain boundaries and thus reduces the chance of pitting corrosion occurring. Another purpose is to provide the aluminum alloy structure itself with anti-corrosion properties that will slow down the progress of corrosion even if it occurs. In this way, the recrystallized grain size of aluminum alloy can be easily controlled by utilizing the following properties of aluminum alloy.

In general, when an aluminum alloy is subjected to hard rolling or drawing, and then heated and recrystallized, the grain size becomes finer, and the lower the degree of cold working, the coarser the grain size becomes.

That is, to obtain a large grain size, the degree of cold working should be reduced, and to obtain a small grain size, the degree of cold working should be increased. With this simple method, the grain size can be reduced to 500.
Aluminum alloys other than aluminum can be obtained, but 50
Corrosion resistance is not improved if the grain size is 0.0 mm or less, and the upper limit is not specified because the larger the grain size is, the better the corrosion resistance is.

It has been shown that the aluminum alloy with a grain size of 500 French or more produced by the method described above exhibits remarkable corrosion resistance compared to the aluminum alloy with a finer grain size that is commonly used. As proof, the results of a corrosion resistance comparison test conducted by the present inventor are described below.

Contents of comparative test m Test piece Test piece Mnl. A plating sheet for an aluminum alloy heat exchanger containing 2% aluminum alloy was vacuum-brazed with fins (the fins were removed leaving only the loaf portion), and the dimensions were 10 x 10 x plate thickness. One of the test pieces had a fine grain size for both the plating sheet and the fins, and the other had a coarse grain size for both.

Test piece details ■ Corrosion test Corrosion test was conducted on P. 4000, CH3COO day. The groove was immersed for 30 minutes in the NaC paste prepared on Day 3, then pulled up to the top of the liquid and dried for 30 minutes with 5,000 yen warm air. This process was continued for one month.

'3' Test Results After the corrosion test was completed, several locations where corrosion was considered to be particularly severe were selected from each test piece, cut out as test pieces, and the cross section was polished and the corrosion status was investigated under a microscope.

Regarding the above table, the micrographs in FIGS. 1 and 2, which correspond to test specimens 1 and 2, respectively, clearly show the corrosion state.

As shown by the above test results, the aluminum alloy for heat exchangers produced by the method of the present invention has remarkable anti-corrosion properties compared to commonly used aluminum alloys for heat exchangers with finer grain size. It is something that demonstrates the.

Brief explanation of the drawings Figures 1 and 2 are micrographs (magnification x
20) to show the respective corrosion conditions.

Figure 1 Figure 2

Claims (1)

[Claims] 1 Mg0.2-2.0%, Fe0.1-1.0%, C
It is an aluminum alloy containing one or more of u0.05~0.4% and Mn0.3~2.0%, and its crystal grain size is An aluminum alloy material for heat exchangers having anticorrosive properties characterized by a thickness of 500μ or more.