JPH03169479A - Method for brazing aluminum material - Google Patents

Abstract

PURPOSE:To simplify brazing process and to reduce the brazing cost by adjusting the inner part of a pre-treating furnace on the atmosphere containing chlorine series gas, pre-treating a joining member held in the atmosphere and then, brazing it in an atmosphere containing no flux of a brazing furnace heated to a prescribed temp. CONSTITUTION:As the coating process of suspension liquid and the drying process after coating are unnecessary at all, the brazing process can be simplified and the productivity can be improved. Furthermore, as the brazing is executed in the brazing furnace containing no flux medium after the pre-treatment in the pre-treating furnace containing the chlorine series gas or chlorine series fine powder particles, the pre-treating time can be set regardless of the brazing time and also the scale of pre-treating furnace can be set smaller than the brazing furnace and consumption of the chloride series gas or chloride series fine powder particles can be reduced and the brazing can be executed at low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for brazing aluminum materials, for example, a method for brazing aluminum materials suitably used in manufacturing aluminum heat exchangers according to brazing specifications.

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

Conventional technology For example, when manufacturing radiators for automobiles, evaporators for car coolers, condensers, aluminum heat exchangers for other electrical appliances and machinery, and aluminum air supply manifolds for automobiles, etc., by brazing, vacuum brazing is used. However, in most cases, a method of brazing heat exchanger components using chloride-based flux is used.

Conventionally, when performing flux brazing, a chloride-based flux is first suspended in water or a solvent, and then this suspension is applied to the surface of the aluminum material to be joined by a spray method, a shower method, a dipping method, etc. This was then preheated and dried to evaporate the moisture, and then heated to a predetermined temperature in a non-oxidizing atmosphere to melt the joining brazing material and perform brazing.

Problems to be Solved by the Invention However, this method requires a suspension coating operation and a drying operation after coating, resulting in poor productivity. Moreover, when the aluminum bonding member has a complicated shape, it is difficult to apply flux automatically, and it is necessary for a worker to apply the flux directly with a brush or the like, resulting in poor workability. Furthermore, since a drying oven is required for drying, there is also the drawback that the equipment becomes large-sized. Furthermore, it was troublesome to control the temperature of the suspension and the amount of application. Furthermore, since the amount of flux that adheres to aluminum materials is generally large, the interior of the brazing furnace may be contaminated, or the flux that has melted in the furnace may drip and accumulate within the furnace, resulting in the need for cleaning the furnace. There was also the problem that overhauls had to be done more frequently. Furthermore, when brazing is performed by applying chloride-based flux, the surface of the aluminum material is etched due to the reaction between the molten flux and aluminum, resulting in uneven color tone and uneven gloss, which impairs the appearance. There was also.

Furthermore, when brazing is performed by applying chloride-based flux, since the flux is corrosive, it is necessary to remove residual residue by cleaning after brazing, and the post-treatment process takes time. There was also.

This invention was made to solve these problems all at once; it eliminates the need for a suspension coating process or preheating drying process, reduces contamination of the brazing furnace by flux, and The object of the present invention is to provide a method for brazing aluminum materials that can simplify the cleaning process and that causes almost no uneven color tone or uneven gloss on the surface of the aluminum material after brazing.

Means for Solving the Problems In order to achieve the above objectives, the authors have conducted various experiments and research, and have found that, before brazing, aluminum is placed in an atmosphere containing chlorine-based gas and fine powder particles of chlorides. We have discovered that good brazing can be achieved by pre-treating the joining members by holding them, and then brazing in a normal atmosphere that does not substantially contain a flux medium such as chlorine-based gas,
This invention was completed based on this knowledge.

That is, in the present invention, the interior of the pretreatment furnace is adjusted to an atmosphere containing chlorine-based gas or chloride-based fine powder particles, and the aluminum bonding member is held in the atmosphere to perform the pretreatment. The finished aluminum bonding members are carried into a brazing furnace that has been adjusted to an atmosphere substantially free of flux media, heated to a predetermined temperature in the brazing furnace, and the brazing filler metal for bonding is melted to perform brazing. It is characterized by the fact that

First, to explain the atmosphere inside the pretreatment furnace, chlorine-based gas and chloride-based fine powder particles act as a flux, which removes the oxide film on the joints and improves the wettability and fluidity of the brazing material during the next brazing process. It exhibits the effect of improving the brazing properties and plays the role of realizing good brazing. Here, the chlorine-based gas includes both chloride gas (CA2) gas and chloride gas (a gasified compound of chlorine and other elements). The specific composition of the chloride gas is not particularly limited. However, the brazing temperature of aluminum is generally 60
Since the temperature is around 0°C, it is preferable to use one that gasifies at 600°C or lower. For example, NaCQ gas, KCΩ gas, BaCJ22 gas, etc. can be suitably used.

As the chlorine-based gas, one type of gas may be used, or a mixture of multiple types of gases may be used.

On the other hand, the specific composition of the chloride-based fine powder is not particularly limited. For example, ungasified Na
Fine powder particles such as C(1, KCp, BaCp2, etc.) may be used. Such chloride-based fine powder particles may also be of one type, or may be a combination of two or more types of chlorides. The atmosphere in the pretreatment furnace containing chlorine-based gas or chloride-based fine powder particles is preferably a non-oxidizing atmosphere. Generally, an inert gas atmosphere such as N2, A', He gas, etc. The atmosphere in the furnace contains chlorine-based gas and chloride-based fine powder particles.If chlorine-based gas is used, the temperature of the atmosphere in the furnace must be below the melting point of the brazing material and at a temperature where the chlorine-based gas maintains its gas state. On the other hand, when using chloride-based fine powder particles, the temperature should be set at a temperature at which the particles do not turn into gas, such as room temperature to 500°C. The content of chlorine-based gas and chloride-based fine powder particles in the atmosphere must be set at a level below the total tO of chlorine-based gas in order to exhibit a good flux effect.
．． It is preferable to set the amount to about 1 to 10,000 ppm, and the total amount of chloride-based fine powder particles to about 20.1 to 10 g/ri. 0.
If it is less than 1 ppn+ or less than 0.1 g/=, it may be too small to exhibit a good flux effect;
Even if it exceeds 0,000 ppm or 10 g/m, the flux effect will be saturated and it will be an economic waste. Particularly preferably, chlorine gas: 1 to 2000 ppm and chloride fine powder particles: 1 to 7 g/TIt. It is also desirable that no moisture or oxygen exists in the atmosphere inside the pretreatment furnace, but H2
0: IOOOOppII+ level or less, 02: 1
If the mixed amount is about 0,000 pp+n or less, it will hardly affect the brazing properties. These are 10000
If it exceeds pplI, the surface oxide film of the aluminum material will become thick, which may hinder good brazing.

The means for adjusting the atmosphere in the pretreatment furnace to an atmosphere containing chlorine-based gas or chloride-based fine powder particles is not particularly limited. A method may be mentioned in which, after mixing, this mixed gas is introduced into a pretreatment furnace. In this case, it is necessary to heat and gasify the chloride, which is liquid or solid at room temperature, in advance. Another method is to gasify the chloride by placing a container containing solid or liquid chloride in a pretreatment furnace and heating it. On the other hand, in the case of chloride-based fine powder particles, for example, finely powdered chloride may be fed together with an inert gas, or suspended in the furnace atmosphere using thermal convection, a stirring fan, a vibrator, etc., or these methods may be used. Examples of methods include appropriate combinations of the following. Alternatively, a method may be used in which a container containing fine chloride powder particles is placed in a furnace and suspended by thermal convection or the like. In either case, the chloride-based fine powder particles are
It is preferable to set the particle size to less than μm. In addition, the flow rate of the inert gas is set to 0.0% as the flow rate in the furnace in order to uniformly stir the chlorine-based gas and chloride-based fine powder particles. 1~10cm/
It is best to set it to sec.

The aluminum bonding member is carried into a pretreatment furnace adjusted to an atmosphere containing chlorine-based gas or chloride-based fine powder particles as described above, and is held in the atmosphere for pretreatment.

The pretreatment time may be about 1 minute, but may be longer or shorter.

The aluminum bonding member that has undergone the above pretreatment is then transported to a brazing furnace. The atmosphere in the brazing furnace is adjusted to be an inert gas atmosphere, such as an N2 gas atmosphere, which does not substantially contain a flux medium such as chlorine-based gas or chloride-based fine powder particles.

Here, "substantially" means to allow the case where trace amounts of chlorine-based gas, chloride-based fine powder particles, etc. are unavoidably included. In this atmosphere, using an aluminum brazing material whose melting point is lower than that of the aluminum bonding material,
By heating to a certain temperature, the brazing material is melted and a good brazed joint is achieved. In this way, good brazing can be achieved simply by holding the aluminum bonding member in an atmosphere containing chlorine-based gas or chloride-based fine powder particles in the pretreatment stage. It is thought that this is because the surface oxide film of the aluminum bonding member has already been removed by exerting a fluxing effect during the pretreatment stage. Further, in the case of chloride-based fine powder particles, it is thought that the particles adhere to the surface of the aluminum bonding member due to pretreatment, and are transported as they are to the brazing furnace where they exert a fluxing effect. The brazing filler metal contains AQ-1 with a Si content of about 4.5 to 13.5 vt%.
A Si-based alloy is usually used, and from the viewpoint of workability, it is usually desirable to use the brazing filler metal as a cladding material on at least one of the aluminum materials of the members to be joined.

Furthermore, the relationship between the pretreatment furnace and the brazing furnace is not a matter that affects the effects of the present invention, and it may be constructed in a continuous type as shown in Figure 1, or in a batch type as shown in Figure 2. It may be set to In the continuous type shown in Figure 1, (1) is a pretreatment furnace, (2) is a brazing furnace, (3) is an inert gas supply device, and (4) is a chlorine-based gas or chloride-based fine powder particles. The chlorine-based gas or chloride-based fine powder particles are mixed with an inert gas and introduced into the pre-treatment furnace (1). (1) It is designed to be uniformly suspended and dispersed. (5
) is an aluminum bonding member, and the aluminum bonding member (5) is transported from the pretreatment furnace (1) to the brazing furnace (
2). In addition, due to the pressure of the inert gas supplied to the brazing furnace (2),
It is designed to prevent chlorine-based gas and chloride-based fine powder particles from entering the brazing furnace (2) from the pretreatment furnace (1). On the other hand, in the batch type shown in Figure 2, (
1') is a pretreatment furnace, (2') is a brazing furnace, (3') (3
”) is an inert gas supply device, (4′) is a chlorine-based gas or chloride-based fine powder particle generator, and (5′) is an aluminum bonding member, which was pretreated in a pretreatment furnace (1′). Once the aluminum joint parts are taken out, they are placed in a separate brazing furnace (
2'). In this case, the pretreated aluminum bonding member (5') is handled in a non-oxidizing atmosphere to suppress the formation of a surface oxide film as much as possible until it is delivered to the brazing furnace (2'). It is desirable to be

Effects of the Invention As described above, the present invention performs pretreatment by adjusting the inside of the pretreatment furnace to an atmosphere containing chlorine-based gas or chloride-based fine powder particles, and holding the aluminum bonding member in the atmosphere. Thereafter, the pretreated aluminum bonding members are transported into a brazing furnace that has been adjusted to an atmosphere that does not substantially contain a flux medium, and heated to a predetermined temperature in the brazing furnace to melt the bonding brazing material. It is characterized by performing brazing. Therefore, first of all, all the disadvantages resulting from the necessity of applying a suspension to the aluminum joint members as in the conventional method can be eliminated. That is, since the suspension coating process and the drying process after coating are completely unnecessary, the brazing process can be simplified and productivity can be improved. Furthermore, since a drying oven is not required, the equipment can be downsized. Moreover, complicated temperature control of the suspension, control of the amount of application, etc. can be made unnecessary, and the efficiency of the entire brazing work can be improved. Furthermore, the amount of chlorine-based gas and chloride-based fine powder particles that act as a flux can be much smaller than that required in conventional coating methods, which is economically advantageous. Since there is less contamination in the processing furnace and there is no possibility of molten flux dripping into the furnace and accumulating in the furnace, the frequency of cleaning and overhauling can be reduced. Furthermore, since the amount of flux attached to the surface of the aluminum material is much smaller than when using the coating method, the surface of the aluminum material is etched due to the reaction between the molten flux and aluminum, resulting in uneven color tone and uneven gloss. This makes it possible to provide high-quality brazed products that are clean and have an excellent appearance without the problem of spoiling the appearance. Since the flux residue after brazing is also reduced, the cleaning process for removing the residue can be omitted or simplified.

Further, since chlorides can be melted and gasified at relatively low temperatures, the present invention can be suitably used for brazing not only aluminum wrought materials but also cast materials with a low melting point.

In addition, in this invention, after pretreatment is performed in a pretreatment furnace with an atmosphere containing chlorine-based gas or chloride-based fine powder particles,
Since brazing is performed in a brazing furnace with an atmosphere that does not contain these flux media, the pretreatment time can be set independently of the brazing time, and in the case of continuous furnaces, the pretreatment furnace The size can be set smaller than that of a brazing furnace, and therefore the amount of chlorine gas or chloride fine powder particles used can be further reduced compared to when the brazing furnace has an atmosphere containing chlorine gas or chloride fine powder particles. This makes it possible to perform brazing at a low cost. Moreover, since chlorine-based gas and chloride-based fine powder particles are not used in the brazing furnace, there is no risk of contamination or damage to the brazing furnace, and there is no need to clean the brazing furnace. No, the cleaning of the pretreatment furnace is slightly simpler than that of the brazing furnace, which is advantageous in terms of workability, economy, etc.

Example Next, examples of this invention will be shown.

(Example 1) NaCfl: 30 ppm was heated and gasified at 595° C. with N2 gas and Ar gas in an electric furnace as a pretreatment furnace.
and KC Dan: 301) I) Ql was introduced.

Next, it consists of an extruded Al 100 tube material with a wall thickness of 0.75M and a double-sided plating sheet with a cladding ratio of 9% and a thickness of 0.15m, with A3003 alloy as the core material and A base-10% St alloy as the skin material. The fin materials were assembled into a corrugated heat exchanger, and this assembly was carried into the pretreatment furnace and held for 30 seconds.

Next, after the assembly was taken out of the pretreatment furnace, it was immediately carried into a brazing furnace adjusted to a mixed atmosphere of N2 gas and Ar gas, and brazed by heating at 605° C. for 5 minutes. In addition, the moisture content in both the pretreatment furnace and brazing furnace is 10
The 0ppm, 02 concentration was 40ppm.

(Example 2) N2 gas, 3 g/rd of NaC powder particles, and 2 g/Trt of Ki powder particles were introduced into a pretreatment furnace at 400° C., and the fine powder particles were floated by thermal convection. After carrying the same assembly as in Example 1 into this pretreatment furnace and holding it there for 1 minute, it was immediately carried into a brazing furnace adjusted to a mixed atmosphere of N2 gas and A gas, and brazed under the same conditions as in Example 1. I followed up. The moisture content in both the pretreatment furnace and the brazing furnace was 50 ppI, and the ISO2a degree was 10 ppl1.

(Example 3) N2 gas and Cn2 gas 3001)I)m were mixed and introduced into the pretreatment furnace. The same assembly as in Example 1 was carried into this pretreatment furnace and held for 1 minute, and then immediately carried into a brazing furnace adjusted to an N2 gas atmosphere, where brazing was performed under the same conditions as in Example 1.

In addition, the moisture content in both the pretreatment furnace and brazing furnace is 60p.
The pm,02 concentration was 20 ppm+.

(Example 4) A pretreatment furnace was equipped with a vibrator and a stirring fan, and B was heated at room temperature.
By vibrating and stirring the fine powder particles of a(122), a N2 gas atmosphere in which the fine powder particles were mixed was formed.The content of Ba(122 fine powder particles in the atmosphere at this time was 7 g/min) The same assembly as in Example 1 was carried into this pretreatment furnace, held for 30 seconds, and then immediately filled with N2
It was carried into a brazing furnace adjusted to a gas atmosphere, and brazed under the same conditions as in Example 1. In addition, the moisture content in both the pretreatment furnace and brazing furnace is 701) I) II The SO2 concentration is 2
It was 0 ppi+.

(Comparative Example 1) A chloride-based flux containing NaCff and K (12 as main components) was suspended in water to create a 5 wt% suspension.The same assembly as in Example 1 was added to this suspension. was dipped, coated with flux, and then dried.

Next, the above brax coated assembly is immediately reduced to a moisture content of 1
00ppn+ S02 concentration was carried into a brazing furnace with an N2 gas atmosphere of 5ppIIl, and brazing was performed by heating at 610° C. for 5 minutes.

For each of the brazed products obtained above, the brazing properties and external appearance were visually observed, and the surface treatment properties were evaluated.

Surface treatment properties are evaluated by spray painting the flat plate part of each brazed product, then marking squares of one angle on the coating surface and performing a tape peeling test, and determining the number of squares where the coating film remains. (checkerboard test). The results are shown in Table 1.

[The following margins are Table 1 (Note 1) (Note 2) (Note 3) Q...Fin bonding rate 100% ×...Fin bonding rate less than 90% 0...Flux residue is confirmed with an inkstone No, the appearance is extremely clean ×...Number of remaining squares/total number of squares of the coating film where residual flux is visually observed.Furthermore, visual observation of the surface gloss of the brazed product revealed that Examples 1 to 3 In contrast to Sample No. 4, which had an even surface gloss over the entire surface, uneven gloss was observed in Comparative Example.

From the above results, according to the present invention, not only good brazing was achieved despite a small amount of chlorine-based gas or chloride-based fine powder particles, but also the obtained brazed product had a good surface condition. I was able to confirm that.

[Brief explanation of the drawing]

FIGS. 1 and 2 are block diagrams showing a schematic structure of brazing equipment as an example of carrying out the present invention. (1) (1')...Pretreatment furnace, (2) (2')...
Brazing furnace, (5) (5')...Aluminum joining member. that's all

Claims (2)

[Claims] (1) Adjust the inside of the pretreatment furnace to an atmosphere containing chlorine gas,
After performing pretreatment by holding the aluminum bonding member in the atmosphere, the pretreated aluminum bonding member is carried into a brazing furnace adjusted to an atmosphere that does not substantially contain a flux medium, and A method for brazing aluminum materials, characterized by heating to a predetermined temperature in a brazing furnace, melting a joining brazing filler metal, and performing brazing. (2) Pretreatment After pretreatment is performed by adjusting the atmosphere in the furnace to include chloride-based fine powder particles and holding the aluminum bonding member in the atmosphere, the pretreated aluminum bonding member is Aluminum is carried into a brazing furnace adjusted to an atmosphere that does not substantially contain a flux medium, heated to a predetermined temperature in the brazing furnace, and brazed by melting a joining brazing material. How to braze materials.