JPS5847266B2 - Corrosion prevention treatment method for aluminum heat exchangers - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an anti-corrosion treatment method for an aluminum heat exchanger, which is made of aluminum and is intended to prevent pitting corrosion and other corrosion peculiar to aluminum.

Conventionally, heat exchangers for automobiles and the like have been mainly made of copper, but aluminum or aluminum alloys have begun to be used because they are lightweight and economical.

In the manufacturing process of aluminum heat exchangers, adhesion of tubes and fins by brazing is essential, and it is known that zinc or zinc alloy coatings are effective in preventing corrosion of aluminum products.

Therefore, the present invention provides a vehicle aluminum heat exchanger that is brazed in a vacuum and is not exposed to the atmosphere after brazing, that is, it is still at a high temperature (150° to 400°C).
The physical vapor deposition method (PVD) is carried out without any pollution in a clean state where surface oxidation does not occur.
This method involves forming a zinc or zinc alloy film on the surface of the product, and performing electrolytic corrosion prevention treatment on the base material together with vacuum brazing in one equipment. As mentioned above, there is a shift from conventional copper exchangers to aluminum exchangers, but when adopting aluminum heat exchangers, there is a need to prevent freezing, especially in cold regions. Corrosion (pitting) problems are occurring due to spraying (Mgcl) on road surfaces or due to salt damage, and currently various anti-corrosion measures are being taken, such as material selection, chemical conversion treatment, anodic oxide coating, and environmental protection through painting. Various countermeasures have been taken, such as cathodic protection, corrosion protection using inhibitors, and flux immersion brazing, but each has its own advantages and disadvantages, and at present no definitive anticorrosion measures have been established.

On the other hand, brazing is an indispensable production technology in the manufacturing process of aluminum heat exchangers, and its methods include brazing in a furnace with a black atmosphere and immersion brazing with a flux. However, all of these methods have the drawbacks of being complicated and expensive, have inferior quality, and have various problems such as flux cleaning waste causing pollution problems.

There are great expectations for fluxless brazing in a vacuum, which eliminates these drawbacks.

Currently, plating sheets such as AA7072 containing zinc have been developed in consideration of the corrosion resistance of aluminum heat exchangers, but when performing vacuum brazing, if the material contains zinc, There is a drawback that vacuum brazing cannot be carried out successfully, and it is desired that vacuum brazing can later form a film of zinc or zinc alloy on the surface of a product economically and without causing pollution.

As mentioned above, it is known that zinc or zinc alloy coatings are effective in preventing electrolytic corrosion of aluminum, and fluxless continuous brazing of aluminum heat exchangers in a vacuum is not possible. It has already been industrialized and put into practical use in the automobile industry and other industries.

The present invention is characterized in that after brazing and cleaning, an appropriate zinc or zinc alloy film is formed on the product in a series of devices of this continuous aluminum heat exchanger brazing furnace. It is.

In this invention, a vacuum evaporation method or an ion blating method is used to form a film of zinc or zinc alloy, and by applying this to a vacuum brazing furnace in one unit, exhaust costs can be reduced and a clean state can be achieved. Excellent adhesion can be expected due to the coating on the product surface, and since there are no foreign substances between the base material and the coating, excellent corrosion resistance can be ensured.

Next, the present invention will be described in detail with reference to the drawings.

In Figs. 1 and 2, a heat exchanger 2 (see Fig. 3), which is a workpiece mounted on a jig 1, is coated with wax appropriately and placed on a frame moving mechanism 3 at point A. The jig 1 is moved from the outside-of-furnace transfer mechanism to the traverser 5, which is moved by the hydraulic mechanism 4, and the preparation chamber 6 and preheating chamber 7 are filled with light oil and sent into the heating chamber 8. vacuum fluxless brazing is performed.

After brazing is completed, the coating chamber 1 is passed through the third gate valve 9.
0, and in this chamber a coating of zinc or zinc alloy is applied.

As shown in FIG. 3, the coating chamber 10 has a guide rail 11 internally provided with a negative high voltage and a heat exchanger 2 connected to the guide rail 11.
A jig 1 supporting the jig 1 runs, and has evaporation sources 14 for zinc or the like made up of a crucible 12 and a heater 13 on both sides thereof.

Since the process is carried out in the continuous vacuum furnace as described above, even after the brazed product is moved to the coating chamber 10, the ion brating or vacuum coating chamber 10 is kept under negative high pressure inside, as shown in Figure 3. A jig 1 supporting the heat exchanger 2 runs on a guide rail 11 to which a voltage is applied, and is provided with an evaporation source 14 of zinc or the like consisting of a crucible 12 and a heater 13 on both sides thereof.

Since the temperature is maintained at 150 to 400°C, which is suitable for vapor deposition, and the product does not leave the vacuum chamber, the surface of the product is kept clean, so that a zinc or zinc alloy film can be efficiently formed.

After coating is completed, the product is transferred to the traverser 16 by the out-of-furnace moving mechanism via the take-out chamber 15, and then transferred to the position of the frame return mechanism 3 by the hydraulic mechanism 17, and then transferred to point B, where the product is transferred from the frame return mechanism 3. removed.

In addition, 18, 19, 20, 21 are other gate valves between each chamber,
22, 23, 24, 25, 26, and 27 indicate exhaust pumps.

This invention involves continuous brazing in a vacuum furnace of one unit.
Since the process involves cleaning and coating, it is possible to efficiently and precisely manufacture vehicle heat exchangers without fear of corrosion.

[Brief explanation of the drawing]

FIG. 1 is an explanatory front view of a one-unit vacuum furnace for carrying out the method of the present invention, FIG. 2 is an explanatory plan view thereof, and FIG. 3 is an explanatory view of a coating chamber. In the diagram: 1... jig, 2... heat exchanger,
5, 16...Transparser-16...
・Preparation room, 7... Preheating room, 8... Heating room, 10... Coating room, 15...
・Removal room.

Claims (1)

[Claims] 1 The process of performing fluxless brazing in a vacuum chamber,
A method for anti-corrosion treatment of an aluminum heat exchanger, characterized in that a process of vacuum deposition or ion-blating of zinc or zinc alloy is performed while there is no temperature drop of the wax body covered in the vacuum state.