JPS61103674A - Production of aluminum brazing article having excellent corrosion resistance - Google Patents

Abstract

PURPOSE:To obtain a good brazing joining with improving the corrosion resis tance of Al brazing article by performing a brazing after precipitating the specific quantity of zinc on the surface of Al material. CONSTITUTION:A zinc is precipitated in 0.6-10g/m<2> on one part or all part of the surface of the joining member made of Al. The flux used for brazing is the mixture of 80-99.8wt% KalF and 20-0.2wt% KF. In case of performing a bracing the flux component is used with suspending in the form of a slurry in the liquid of water, etc. and this suspension is uniformly coated on at least either one part of the joining member made of Al. A brazing joining is achieved with drying after the coating and with heating to the temp. lower than the melting point of the joining member and higher than the melting point of the flux in the nonoxidizing atmosphere of inert gas atmosphere etc. with using the Al alloy brazing filler metal having lower melting point than the joining member.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a method for producing aluminum brazed products with excellent corrosion resistance, and in particular to a method for producing aluminum brazed products that are suitable for producing aluminum heat exchangers due to their brazability. Regarding the manufacturing method.

In this specification, the term aluminum is used to include its alloys.

Conventional technology and problems Conventionally, when manufacturing aluminum heat exchangers such as automobile radiators, car cooler evaporators, or condensers using flux brazing properties, chloride-based fluxes containing zinc chloride, etc. were used. A method of brazing and joining heat exchanger components is known.

At the same time as each member is joined by brazing, zinc is precipitated on the surface of the component member by brazing heat and diffused into the member, and due to the sacrificial r9J polar effect of the zinc diffusion layer, the heat exchanger This is because it is also expected to improve corrosion resistance.

However, in this method, since the flux used is essentially water-soluble and has strong hygroscopic properties, it is necessary to immediately wash away any remaining flux during brazing. However, this method has the drawbacks of high equipment costs, complicated processes, and a heavy workload.

Moreover, if the residual flux was not completely removed, there was a risk of corrosion. Moreover, since the diffusion layer is formed by using a small amount of zinc contained in the flux, it is not only impossible to form a sufficient diffusion layer, but also in complex assemblies such as heat exchangers. Since it is difficult to uniformly apply the flux, the zinc diffusion layer also becomes non-uniform depending on the location, and therefore, it is not possible to exhibit a sufficient anticorrosion effect.

On the other hand, as a brazing method that does not require flux cleaning as described above, fluoroaluminium complex salts (K3AgF2 and KAρFa) added with zinc or zinc fluoride, etc.
A method of brazing using a non-corrosive fluoride-based 7-lux with a composition of Although LC forms a layer, there still remains a problem in terms of anti-corrosion effect. However, this brazing method has problems (and also in terms of the ease of manufacturing the flux to be used).

In other words, this brazing method generally requires that the composition ratio of fluxes that are actually produced and used industrially be as close as possible to the eutectic point of KAQF4 and 3AΩF6, which have a low melting point. The reality is that it is set. This is based on the general requirement that the melting point of the flux should preferably be about 10 to 20 degrees Celsius lower than the melting point of the brazing filler metal, and within this range, it is practically preferable to have a lower melting point. However, in many cases, the method for producing flux that achieves such a composition ratio uses AQF3 and KF as starting materials, and mixes the starting materials with KAQF4, which is a eutectic mixture thereof, and 3 AgF2 as described above. The method used is to mix in a dry state in an appropriate ratio to achieve the desired ratio, melt this mixture, and roughly cool and solidify the molten mixture, which requires a large number of man-hours. There was a problem that preparation was troublesome.

In view of the above-mentioned matters, this invention has developed a non-corrosive flux that is easy to prepare, thereby eliminating the need for de-fluxing treatment, providing excellent sacrificial corrosion protection effects for aluminum materials, and making it as simple as possible. The present invention also aims to provide a method for manufacturing aluminum brazed products that is low-cost and has excellent corrosion resistance.

A means for solving the problem, that is, a method for manufacturing an aluminum brazed product with excellent corrosion resistance according to the present invention, is to precipitate zinc at 0.6 to 10 g/m on a part or all of the surface of a joining member made of aluminum. After that, KANF+: 80-99.8wt%, K
F: A suspension of a flux consisting of a mixture of 20-0.2 wt% in a liquid such as water is applied to the bonding member and dried, and then heated to a predetermined humidity in a non-oxidizing atmosphere. , which is characterized by melting and brazing a joining brazing material.

In this invention, first, 0.6 to 10 y of zinc is applied to part or all of the surface of a bonding member made of aluminum.
/Td shall be precipitated.

The reason why the amount of zinc precipitation is limited to the above range is that the amount of zinc precipitation is 109
This is because if it exceeds 0.6 ej/m, the surface zinc concentration after brazing will increase, resulting in faster initial corrosion and shorten the sacrificial corrosion protection period. This is because the corrosion resistance decreases and a sufficient sacrificial corrosion protection effect cannot be obtained.

As the zinc deposition method, any known method such as chemical displacement plating, electroplating, hot-dip plating, etc. may be employed.

Brazing shall be performed after this zinc precipitation.

The flux used for this brazing is KAQF4: 80~
It is a mixture of 99.8 wt% and KF: 20 to 0.2 wt%. The purpose of adding KF to KAQF4 is to lower the melting point of the flux and make it work more effectively during brazing heat19.If KF is less than the allowable lower limit, the effect will be poor; If too much of the flux is mixed, the melting point will rise, making it impossible to perform good brazing, and even worse, the flux reaction 1flllffi will exceed the melting point of aluminum as a joining member, resulting in poor brazing. itself may become impossible. This flux is prepared by mixing KAlF4 and KF in the above ratio.
3. Since KF is also traded as a commercial product and is easily available, fluoroaluminum tin salts (Kl A base F6 and KAQF4) are generally produced using AQF3 and KF as starting materials from the viewpoint of ease of preparation. This is extremely advantageous compared to fluoride-based fluxes that have a composition of Furthermore, since the flux used in this invention is non-corrosive after brazing, it does not affect the corrosion resistance of the product in any way even without de-flux treatment.

When performing brazing, the flux component is used by suspending it in the form of a slurry in a liquid such as water, and this suspension is uniformly applied to at least one of the joining members made of aluminum. In order to facilitate suspension and application in this liquid and improve brazing properties,
The powder particle size of the flux component is preferably approximately 200 uTrL or less. Although spraying or brushing can be used as the above-mentioned application method, it is recommended to use a dipping method as a uniform application method suitable for mass production.

The joining member made of aluminum is dried after applying the above-mentioned flux, and then the melting point of the joining member is adjusted in a non-oxidizing atmosphere such as an inert gas atmosphere using an aluminum alloy brazing filler metal whose melting point is lower than that of the joining member. By heating to about 580-620° C., which is lower and above the melting point of the flux, the braze metal is melted and a brazed joint is achieved. The brazing filler metal has a Si content of about 45 to 13,5
Usually, about wt% of Aρ-3i alloy is used, and from the viewpoint of workability, the brazing filler metal is usually used as a cladding material for at least one aluminum component of the members to be joined. It is. Along with the heating during this brazing step, the zinc deposited on the surface of the aluminum material is diffused toward the center of the aluminum material, and a uniform and sufficient zinc diffusion layer is formed on the surface of the aluminum material.

The layer thickness of this diffusion layer is 50LtTrL from the viewpoint of corrosion prevention effect.
It is desirable that it be above.

Effects of the Invention According to the implementation of the present invention as described above, since zinc is precipitated on the surface of the aluminum material and then brazed, the heating in the brazing process coats the surface of the aluminum material uniformly and sufficiently. A zinc diffusion layer can be formed, and the sacrificial anode effect of this zinc diffusion layer can significantly improve the corrosion resistance of aluminum solder parts such as heat exchangers.

In addition, in this invention, KAlF4 and K are used as fluxes.
By using a mixture with F, extremely good brazing joints of aluminum materials can be achieved. In other words, the flux exhibits excellent flux effects such as destroying oxides on the surface of the joint and promoting wetting and spreading of the brazing material, making it possible to form a strong soldered joint, and especially superior to vacuum brazing. It can demonstrate its adhesion. Moreover, since the flux used in this invention is non-corrosive after brazing, there is no need to wash and remove the flux residue after brazing, unlike when using conventional chloride-based flux. Therefore, it is possible to manufacture products using aluminum brazing in a completely bonded state with excellent corrosion resistance while simplifying a series of brazing work processes and reducing manufacturing costs.

Furthermore, the flux used in this invention includes KAlF4,
Since both KF and KF are easily available separately as commercial products,
Since it can be easily prepared by mixing these as starting materials, it does not require a complicated preparation process like the conventional 3AQFs-KAρF4 flux that uses AQF3 and KF as starting materials, and can be easily prepared. It also has a lasting effect.

EXAMPLESNext, in order to clarify the advantages of the present invention, several examples thereof will be shown in comparison with various comparative examples.

A hollow, flat extruded tube material made of Al100 alloy with a wall width of 0.8 mm is bent into a serpentine shape with a straight pipe section, and a 1.5 mm thick extruded tube material made of A1100 alloy is sandwiched between the tube material on both sides. Place O1/lIn side plate, then BA
A corrugated fin material made of a double-sided plating sheet with a thickness of 0.145 m (A3003 alloy core material clad with A4343 alloy skin material on one side at a cladding rate of 10%) represented by 12 was attached to the side plate and extruded tube material. and between the straight pipe portions of the tube material, and assembled into an IJ--Bentine type heat exchanger.

Then, the heat exchanger assembly was heated with NaOH: 300 g/Q.
, Zn O: 60 g/Q were immersed in an aqueous solution at 27° C. to precipitate zinc in amounts shown in samples Nos. 011 to 7 in the table below, and washed with water.

Next, water was added to the fluxes of various compositions shown in Samples No. 1 to 7 in the table below to form a suspension with a concentration of 10%, and zinc was precipitated in this suspension. Objects were soaked and dried.

After that, each of the above assemblies was heated to 605°C for 5 minutes using N2 gas in a furnace adjusted to a dew point of -40°C to perform brazing, and then the A7N○1 union was soldered in place using a torch. I installed a 1q car cooler heat exchanger.

Then, the condition of the brazed heat exchangers obtained above was examined, and in order to examine their corrosion resistance, J15-
A CASS test based on H-8681 was conducted. The results are shown in the same table.

[Left below] Brazing condition: O...Good ×...Poor As is clear from these results, in the case of samples Nos. The time it takes for a through hole to occur in the tube material is 2000
It lasted for more than 30 hours and had excellent corrosion resistance. On the other hand, sample No. 5 in which the Zn precipitation does not reach the range of the present invention
In this case, although the brazing was in good condition, through holes were formed in the tube material after 680 hours. In addition, sample No. 016 in which the amount of 7n precipitation exceeded the range of the present invention
In this case, the initial corrosion was severe and the fin material was severely eroded after 100 hours. In addition, sample No. 097 whose flux composition deviates from the range of the present invention
In these cases, brazing itself was impossible.

On the other hand, a comparison with a conventional method using a ZnF-containing fluoride flux showed the following results.

A ZnF-containing fluoride blank having the composition shown in sample N008 in the table is made into an aqueous suspension with a concentration of 10%.
-n After the assembly of the tube material and fin material which had not been subjected to the precipitation treatment was immersed and dried, brazing was performed using the same thread gauging as described above to obtain a heat exchanger. Although the brazing of this heat exchanger was in good condition, shell holes were formed in the tube material after about 590 hours in the CAST test.

From the above results, it was confirmed that according to the present invention, a heat exchanger with good brazing condition and extremely excellent corrosion resistance could be manufactured.

that's all 3871

Claims (1)

[Claims] After depositing 0.6 to 10 g/m^2 of zinc on part or all of the surface of the joint member made of aluminum, K
AlF_4: 80-99.8wt%, KF: 20-0.
Applying a suspension of a 2 wt% mixture of flux in a liquid such as water to the joining member and drying it;
A method for manufacturing aluminum brazed products with excellent corrosion resistance, which comprises heating to a predetermined temperature in a non-oxidizing atmosphere to melt a joining brazing material and brazing.