JPS6050861B2 - Aluminum material for brazing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an aluminum material which is subjected to zinc displacement plating and then brazed. In particular, the present invention relates to an aluminum material which is subjected to zinc displacement plating and then brazed.
A precipitated layer is obtained, and during subsequent brazing, Zn diffusion treatment can be performed at the same time to obtain excellent corrosion resistance.

Generally, flux brazing, vacuum brazing, inert gas brazing, etc. are used to manufacture aluminum heat exchangers for automobiles.

The flux brazing method is not only expensive due to the use of expensive flux, but also has problems with the disposal of washing waste liquid, and recently there has been a shift to vacuum brazing methods and inert gas brazing methods. In the flux brazing method, precipitation and diffusion of Zn from the flux occurs, and the diffusion layer acts as a sacrificial anode to prevent pitting corrosion, resulting in full-scale corrosion, so it takes considerable time for pitting corrosion to reach penetration. It takes time.

However, heat exchangers made using vacuum brazing or inert gas brazing do not have a Zn diffusion layer that serves as a sacrificial anode, so pitting corrosion may occur if they come into contact with a harsh corrosive environment, which can lead to penetration in a short period of time. . Recently, in an inert gas brazing method, a method has been proposed in which zinc displacement plating is applied to the surface of an Al material in advance, and this is brazed to simultaneously diffuse Zn.

Pure N)Al-Mn alloys are generally used as Al materials, but when these materials are subjected to zinc displacement plating, Zn
The variation in precipitation is very large, making it difficult to control the amount of Zn precipitation, making it unsuitable for actual operation. In order to improve this, methods of etching the surface of the N material with caustic soda or degreasing with only a solvent have been attempted, but etching with caustic soda reduces the amount of Zn precipitation to less than 5 y/d, and the required amount of precipitation, That is, if you try to apply around 15g/I, abnormal precipitation such as blisters will occur. Further, when degreasing with only a solvent, the target product of around 15 y/d can be easily obtained, but there is a drawback that the amount of precipitation is large and manufacturing control is difficult. In view of this, the present invention applies zincate treatment (50y/
lZnO) 370y/lNaOH) liquid temperature 35°C for 5 minutes, Zn precipitation amount 15y/d) was carried out to investigate the variation in the Zn precipitation amount and its cause, and to confirm that the cause of the variation is the amount of trace impurities and added elements. As a result of further investigation, we developed an aluminum material for brazing that has excellent zinc substitution properties, and has a FeO. l5~0.50Wt% (hereinafter referred to as Wt
% is simply written as %.

), CUO. OO5~0.10%, Al99.3O~9
This relates to an aluminum material consisting of 9.70% and the remainder being unavoidable impurities. That is, the present invention has investigated the causes of variations in the amount of Zn precipitated in zinc displacement plating of pure A1 and A1-Mn alloys, and has found that, in particular, Mn. Fe. ．． The influence of Cu is large, and when Mn is added, the amount of Zn precipitation decreases,
In order to deposit the target 15y/7T1, it is necessary to more than double the processing time. On the other hand, increasing the processing time may cause abnormal precipitation such as blisters, so A1-Mn alloy is used as the material for zinc substitution plating. is undesirable, and even in pure N, the influence of small amounts of Fe and Cu is particularly large.Furthermore, for pure A1, which is a conventional material, the lower limit of A1 purity and the upper limit of impurities are specified by the JIS standard, but in reality The composition of commercially available pure N varies considerably, and when zinc displacement plating is performed using such materials, Zn
The amount of Zn precipitated varies greatly, and although it is possible to control the amount of Zn precipitated to some extent in the laboratory, it is extremely difficult to control it in actual operation.Based on this, we conducted further studies and found that content 0.15-0.50%, Cu
Content 0.005-0.10%, A1 purity 99.3
By regulating the amount to 0 to 99.70%, a uniform zinc precipitation amount of 15±3 y/d was obtained by zinc displacement plating, especially the above-mentioned zincate treatment. -Yes.

Incidentally, Mn. Mg. Znlcr. ．．
It is desirable that Tl and the like be each 0.01% or less. However, the reason why the components of the aluminum material of the present invention are limited as described above is as follows.

2 Fe content 0.15-0.50%, Cu content 0
．． The reason for setting the content to be 0.005 to 0.1% is that if either Fe or Cu is below the lower limit, the amount of ZIfr produced will vary widely and abnormal precipitation such as blisters will easily occur. Furthermore, when either Fe or Cu exceeds the upper limit, the amount of ZnJfT deposited is small due to the zincate treatment, and the amount of deposited is reduced to 15±3y.
/Rrl, and a sufficient Zn diffusion state cannot be obtained by brazing, and pitting corrosion cannot be completely prevented. In addition, the reason why the A purity is set to 99.30 to 99.70% is because if it is less than 99.30%, the amount of Zn precipitation will be low.
．． If it exceeds 70%, the amount of Zn precipitation and variation will increase,
Moreover, this is because abnormal precipitation such as blisters is likely to occur.

The aluminum material of the present invention has the above composition and is applicable to various brazing materials, and is particularly effective as an extruded tube material.

Further, for zinc displacement plating, it is desirable to use zincate treatment using alkaline sodium zincate, and the surface may be adjusted using only a solvent during the treatment. In addition, as a brazing method, an atmosphere where Zn does not evaporate, such as N2
Brazing is performed without using flux in a gas atmosphere, but brazing is performed using a flux that does not contain ZnCl2 in N2 gas or air, or
The high vacuum brazing (10-
4T0rr or less) cannot be applied, but low vacuum brazing that introduces a small amount of N2 gas (10-3T0rr or more) is applicable to some extent.

Examples of the invention aluminum material will be described in detail below. N having the composition shown in Table 1 is melted and cast into a mold,
A billet with a diameter of 18 mm and a length of 40 hours was obtained.

This was heated to a temperature of 550°C and extruded at a temperature of 500°C to obtain a wall thickness of 1.0Tr0rL1 width 30mm as shown in Figure 1.
7110! , height 5? A multi-hole tube was manufactured. After degreasing these tubes with Triclean, seal the holes in the tubes with tape to prevent the liquid from entering inside, and then remove the ZnO5
The sample was treated for 5 minutes in a zincate treatment solution containing Oy/' and NaOH37Oq/f at a temperature of 35°C.

In addition to investigating the amount of Zn precipitated in these cases, the tubes were heated at a temperature of 600°C in an N2 gas atmosphere for 55 minutes to simulate brazing.
After heat treatment for a minute, pitting corrosion was measured by conducting a casing test and an alternating wet/dry test. These results are also listed in Table 1.
The amount of Zn precipitated was determined by immersing the sample in a 10% HNO3 solution at room temperature for 1 minute to elute Zn, and then weighing the weight before and after that.

Also, the Ciyasu test is 72CRi! In the intermittent dry/wet alternating test, one cycle was immersion in a 5% NaCl solution for 1 min, followed by drying at a temperature of 50°C for 5°C @ 1000°C.
After each cycle, the occurrence of pitting corrosion was examined, and those in which pitting corrosion stopped within the Zn diffusion layer (approximately 0.15 Tm1n) were marked with an O symbol, indicating that the sacrificial anode effect was sufficient.
Those in which pitting corrosion has progressed beyond the Zn diffusion layer are marked with an x mark, indicating that the sacrificial anode effect is insufficient. As is clear from Table 1, the present invention A1 materials (NO.1 to NO.7) have a Zn precipitation amount of 12 to 18y/d1, that is, 154±3y/R.
fl is within the range, and it can be seen that the pitting corrosion resistance after brazing is excellent in both cases.

On the other hand, the comparative A1 material (NO68), which has a higher N purity than the present invention A1 material, and the comparative alloy (NO.1), which has a lower Fe content,
In the comparative alloys (NO.l2) with low Cu content, the amount of Zn precipitated increases and abnormal precipitation due to blistering causes Zn to not contribute sufficiently to diffusion even when heated for brazing. Comparative A1 material (NO.9) with poor pitting corrosion resistance and lower A1 purity than the present invention AI material, comparative alloy with high Fe content (NOll), comparative alloy with high Cu content (NO13), and 1100111 material. Conventional alloy (N
O. l4), conventional alloys of 3003111 are all Z.
It can be seen that the amount of n precipitation decreases and the pitting corrosion resistance after brazing is also poor.

As described above, according to the aluminum material of the present invention, the amount of Zn precipitation can be reduced to 15±3 by zinc displacement plating, especially zincate treatment.
Since the Zn diffusion layer can be sufficiently controlled within the range of d/d, a Zn diffusion layer which becomes a sacrificial anode is formed during subsequent brazing, which has a remarkable effect of improving corrosion resistance after brazing.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing a multi-9-hole tube for a heat exchanger formed by extrusion.

Claims (1)

[Claims] 1 Fe0.15~0.50Wt%, Cu0.005~
0.10 Wt%, Al99.30-99.70 Wt%,
An aluminum material for brazing with excellent zinc displacement plating properties, with the remainder being unavoidable impurities.