JP3203205B2 - Aluminum brazing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flux brazing method for an aluminum material, and more particularly to a brazing method suitable for simultaneously joining a plurality of brazed portions in one brazing step.

[0002] In this specification, the term "aluminum" is used to include an alloy.

[0003]

2. Description of the Related Art In general, when there are several hundred brazing points in one product, such as a heat exchanger, a brazing sheet is used for components such as plates and fins, and after assembling each member, the furnace is installed. Heating is performed, and brazing is performed at a plurality of locations in a single heating step. Further, when using a flux in such a furnace brazing, a flux suspension in which a non-corrosive fluoride-based flux is dispersed in a liquid is applied to a joining member by spraying or dipping, and then dried. Assembling of each component is performed.

Conventionally, water has been generally used as a dispersion medium of the flux suspension. However, water has an extremely low viscosity, so that the adhesion of the flux to the joining member is poor. there were. If the adhesion is poor, the flux tends to fall off when friction or vibration is applied to the coating surface in the process after coating, which leads to a deterioration of the work environment and a decrease in brazing properties due to the scattering of the flux, and the circuit of the heat exchanger If they fall into the interior, they will become residual foreign substances. In addition, since the amount of water flowing down during application is not small, brazing can be improved by applying an extra amount in anticipation of the amount of loss, but the amount of flux residue remaining on the member surface after brazing increases, However, if the adhesion of the coating film is deteriorated, or if a large amount of residue is moisturized, the corrosion resistance is deteriorated and an unpleasant odor is generated. Further, there is another problem that the residue remaining inside the circuit increases the resistance of the passage of air or refrigerant, thereby lowering the heat exchange function.

[0005] Therefore, various paste-like flux compositions have been proposed in which the viscosity of the flux suspension is increased to improve the adhesion of the flux. For example, Japanese Patent Application Hei 8-1
In JP 87594, a viscous vehicle in which a polyalkylene oxide serving as a resin binder is dissolved in an organic solvent is used as a dispersion medium. The polyalkylene oxide is characterized in that a suitable viscosity can be obtained by dissolving it in a solvent, and that it has good thermal decomposability and does not produce a carbonized residue after brazing. Such a flux paste is applied to a joint, heated and evaporated or decomposed to remove the vehicle component, and then brazed by a conventional method.

[0006]

However, the organic solvent has a peculiar odor, and there is a problem that the odor gives an unpleasant sensation to an operator particularly when heated. Also, among the organic solvents used in the above-mentioned flux paste,
Some of them, such as 1,4-dioxane, are highly flammable and dangerous, and may be harmful to the human body. Furthermore, if it remains at the joint as undecomposed matter, it may cause deterioration of brazing properties.

[0007] The use of a viscous vehicle as a dispersion medium has improved the adhesion of the flux as compared with the case where the flux is dispersed in water. Some of the flux that has fallen off from the joints, and the above-mentioned problems caused by the dropped flux have not yet been completely solved.

The present invention has been made in view of such technical background,
It is an object of the present invention to provide a method of brazing an aluminum material, in which a proper amount of flux is supplied to a joint portion without any excess or shortage at the time of brazing and a working environment can be improved.

[0009]

According to the present invention, there is provided a method for brazing an aluminum material, comprising the steps of: providing a fluoride-based flux; 5 to 30% by weight;
A polymer composition containing 5 million alkylene oxide repeating units; a flux composition containing 0.5 to 70 wt% and the balance water is applied to an aluminum material for joining, and then the application surface is heated to obtain a water content. Is removed, and then the application surface is heated to decompose and remove the polymer compound, and then heating for brazing is performed as a basic gist.

The type of aluminum material that can be brazed by the method of the present invention is not limited as long as brazing using a fluoride-based flux described below is possible. Also, the brazing material to be used is not limited at all as long as brazing using a fluoride-based flux described later is possible.

The flux composition used in the present invention uses water as a dispersion medium and a water-soluble polymer compound as a binder to impart viscosity to the composition and improve the adhesion of the flux to the joint. ing.

The high molecular compound has an alkylene oxide repeating unit such as ethylene oxide or propylene oxide, and may be a homopolymer of alkylene oxide, a copolymer of another alkylene oxide or a copolymer with another compound. good. Also,
Both linear and branched polymer compounds can be used.
A more preferred polymer compound is a polyalkylene oxide compound obtained by addition polymerization of a lower alkylene oxide such as ethylene oxide to an organic compound having two or more active hydroxyl groups, or a polyalkylene carboxylic acid, an anhydride thereof or a polyvalent carboxylic acid thereof. A polymer compound obtained by reacting with a lower alkyl ester or a diisocyanate. The terminal of the molecule has an alkoxy group, a carboxyl group, or an ester group in addition to a hydroxyl group, and has an ester bond or a urethane bond other than an ether bond in the molecule.

Examples of the organic compound having two or more active hydroxyl groups include polyhydric alcohols such as ethylene glycol, propylene glycol, 1,3-butylene glycol, glycerin, trimethylolpropane, and pentaerythrol, hydrogenated bisphenol, bisphenol dihydroxyl. Examples include polyhydric phenols such as propyl ether. The polycarboxylic acids include maleic acid, fumaric acid, succinic acid, gluconic acid, adipic acid, sebacic acid,
Examples include isophthalic acid, terephthalic acid, trimellitic acid and the like.

It is necessary to use a polymer having a number average molecular weight of 50,000 to 5,000,000. If the number average molecular weight is less than 50,000, sufficient viscosity cannot be obtained unless a large amount of the polymer compound is used, resulting in poor economy. 5
If it exceeds 100,000, the spinnability becomes too strong, and the viscoelastic properties deteriorate. The preferred lower limit of the number average molecular weight of the polymer compound is 300,000, and the preferred upper limit is 500,000.

The fluoride-based flux used in the present invention includes AlF ₃ -KF and KAlF ₄ -K
₃ AlF ₆ , K ₃ AlF ₆ , KAlF ₄ , KF-AlF
₃ -Al ₂ O _3, can be exemplified _Cs x _Al y _{F z.}

In the flux composition used in the method of the present invention, the content of the fluoride-based flux is 5 to 5.
30% by weight. If the amount is less than 5 wt%, the amount of flux supplied to the joint is small, so that there is a possibility that a brazing defect may occur. On the other hand, if it exceeds 30% by weight, the appearance quality of the product deteriorates, such as the formation of white residue and black spots of the flux after brazing. The preferred lower limit of the fluoride flux is 10
wt%, and a preferred upper limit is 20 wt%. Also,
The content of the polymer compound is 0.5 to 70% by weight.
If it is less than 0.5 wt%, sufficient viscosity is not exhibited, and it becomes difficult to supply a required amount of flux to the joint. on the other hand,
If it exceeds 70 wt%, the water content becomes relatively small, the viscosity of the composition becomes too high, and the amount of the polymer compound attached to the joint becomes large, so that it takes a long time for thermal decomposition. In addition, inconveniences such as an excessive amount of flux adhesion and poor coating workability also occur. The preferred lower limit of the content of the polymer compound is 1 wt%, and the upper limit is 3 wt%. Also,
The content of the polymer compound can be set based on the viscosity of the flux composition. The preferred viscosity of the flux composition is 150 to 500 cps at 23 ° C., and the content can be set such that the viscosity falls within this range in consideration of the number average molecular weight of the polymer compound used.

In the flux composition, the balance of the two components is water. Since water is odorless and has no volatility, it does not deteriorate the working environment unlike an organic solvent, and is safe for the human body.

Further, in the flux composition of the present invention, it is preferable to add a surfactant to enhance the dispersibility of the flux. The types of surfactants are polyoxyethylene glycol, polyoxypropylene glycol, polyoxyethylene polyoxypropylene glycol, polyoxyethylene alkyl phenyl ether, because they have a good affinity for fluoride flux.
Polyoxyethylene alkyl ether, glycerin fatty acid ester, sorbitan fatty acid ester, pentaerythritol fatty acid ester, polyoxyglycene fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxypentaerythritol fatty acid ester,
Nonionic ones such as polyoxyethylene alkylamino ether and polyoxyethylene polyoxypropylene glycol of ethylenediamine are preferred. In addition, the amount of addition is flux / nonionic surfactant = 1 to 1 in weight ratio.
A range of 1000 is preferable, and a range of 5 to 500 is particularly preferable.

In the present invention, the aluminum material is brazed by the following steps using the above-mentioned flux composition.

First, the flux composition is applied to a joint of an aluminum material. The application method may be a known method such as spraying or dipping, and is not particularly limited. The coating amount is preferably about 1 to 3 g / m ^{2 in} terms of fluoride flux.

Next, the coating surface is heated to evaporate and remove only the moisture of the flux composition, thereby losing the fluidity of the composition and causing the flux to adhere to the joint by the adhesive force of the polymer compound. In this heating, it is necessary to remove water and not to thermally decompose the polymer compound. Therefore, the temperature is lower than 150 ° C. which does not decompose the polymer compound, particularly 100 to 13 ° C.
0 ° C. is preferred. The heating time is preferably about 1 to 10 minutes.

Next, an operation of applying friction and vibration to the aluminum material is performed. For example, transportation of the flux composition from the application work place to the assembly work place, assembling, transportation from the assembly work place to the thermal decomposition step of the polymer compound, and the like. Since the flux is strongly adhered to the joint by the action of the polymer compound, there is no possibility that the flux will fall off even when friction or vibration is applied.

Next, the surface to which the flux composition is applied is heated to thermally decompose the polymer compound and remove it from the joint, so that only the flux is present at the joint and prepared for brazing. If the polymer compound remains in the joint, the decomposition residue of the polymer compound is taken into the fillet due to high-temperature heating for brazing in the next step, which may reduce the joint strength. . In this heating,
Since it is necessary to thermally decompose the polymer compound and not to melt the brazing material, it is preferable to heat at 150 ° C. or more for 5 minutes or more. Particularly, the temperature is preferably 150 to 200 ° C or lower. When heated at this temperature for more than 5 minutes, 9
0% or more is decomposed, and only the flux adheres to the joint. In this state, since the adhesive force of the polymer compound has been lost, no friction or vibration is applied to the coated surface.

Further, when heating for brazing is further performed, good brazing is achieved by the action of the flux.

[0025]

EXAMPLES Next, specific examples of the method for brazing aluminum materials according to the present invention will be described.

A flux composition was prepared by mixing the respective materials at the ratios shown in Table 1 below.

[0027]

[Table 1]

These flux compositions were examined for adhesion to aluminum materials and for the presence of unpleasant odor during heating.

The adhesion test was carried out by applying a flux composition of 2.5 g / m ^{2 on a} flat test piece of JIS A3003.
And dried by heating at 120 ° C. for 5 minutes, and the coated surface was rubbed with a cloth. Those having a flux peeling area of 10% or less were accepted. The test results are shown in Table 1.

Further, a brazing test was performed using the above flux composition.

The brazing test was performed by manufacturing the heat exchanger (A) shown in FIGS.

In the overall view of the heat exchanger (A) shown in FIG. 1, (1) is a plurality of flat tube elements stacked vertically and in the left-right direction, and (2) is an adjacent tube element ( 1) Corrugated fins arranged between (1) and outside the outermost tube element (1) and integrated by brazing. Each of the tube elements (1) has bulging tank portions (3a) and (3b) at both ends in the length direction, and has both tank portions (3a) and (3b) at an intermediate portion in the length direction. It has a plate portion (5) that forms a flat refrigerant passage (4) that communicates with the plate portion (5). Each of the tube elements (1) is brazed and joined in an abutting state at the tank portions (3a) and (3b).
a) Adjacent tanks are in communication with each other via refrigerant flow holes (6) and (6) provided in (3b).

The corrugated fin (2) is JIS
A sheet made of A3203 and having a thickness of 0.12 mm is formed into a required shape.

Each of the tube elements (1)
Are formed by laminating two dish-shaped core plates (7) facing each other at their peripheral end joining surfaces (7a) and brazing them together. The core plate (7) is formed by shaping a brazing sheet in which a cladding material of JIS A4343 is clad on both sides of a core material of JIS A3003 having a thickness of 0.4 mm at a cladding rate of 12% to a required shape.

As shown in FIG. 2, the core plate (7) has outwardly protruding cup portions at both ends except for an outer core plate (7 ') constituting the outermost tube element (1). (10) is formed, and three coolant circulation holes (6) are formed in the top wall. The outer core plate (7 ') of the outermost tube element (1) is flat at both ends, and has three refrigerant flow holes (6) at the lower end. Then, such two core plates (7) (7) or (7)
The tanks (3a) and (3b) are formed in the cup portion (10) by overlapping the (7 ′) in opposition, and the tank of the adjacent tube element (1) through the refrigerant flow hole (6) is formed. The parts (3a) (3a) or (3b) (3b) are in a communicating state.

On the other hand, on the inner surface of each core plate (7), one cup (10) is connected to the other cup (10).
Inwardly protruding ribs (11) are formed at predetermined intervals in the width direction of the core plate (7).
Then, by superposing the two core plates (7) and (7) having the ribs (11), the peripheral end joining surface (7) is formed.
a) The two plates are joined together, and the ribs (11) (11) of the core plates (7) (7) are alternately arranged, and the tips of the ribs (11) face each other. The ribs (11) of the core plate (7) are joined in a staggered arrangement in contact with the flat portions (12) between the ribs (11), and are inserted into the refrigerant passages (4) of the tube element (1).
A plurality of unit refrigerant passages extending straight from the lower tank portion (3b) toward the upper tank portion (3a) are formed.

As shown in FIG. 1, a plurality of tube elements (1) as described above are arranged such that corrugated fins (2) are interposed therebetween, and the adjacent ones are placed in a tank. The parts (3a) and (3b) are brazed and joined in a contact state. Here, the core plate (7)
The mutual bonding is performed via the inner skin layer of the core plate (7), and the connection between the tube element (1) and the corrugated fin (2) is performed via the outer skin layer of the core plate (7). . Also, the adjacent tube element (1)
(1) The joining is performed via the outer skin layer of the core plate (7). In FIGS. 1 and 2,
(14) and (15) are a refrigerant inlet pipe and a refrigerant outlet pipe which are connected to the lower tank portions (3b) of the left and right outermost tube elements (1) through the refrigerant flow holes (6), respectively. (16) are side plates arranged outside the outermost corrugated fins (2), and these side plates (16) are also the core plate (7).
And brazed to the outermost corrugated fins (2).

That is, in this brazing test piece, A3003 is connected to A4 at the opposing contact portion of one set of core plates.
343 brazing material, and A3003 is provided at the contact portion between the outer surface of the tube element and the corrugated fin.
And A3203 are similarly joined by brazing with an A4343 brazing material.

Each member was brazed by combining any of the flux compositions shown in Table 1 above with the following two types of steps. Table 2 shows the types of the flux composition and the combinations of the steps.

[0040]

[Table 2]

[Step I (Method of the Present Invention)] A predetermined amount of the flux composition was spray-coated on the core plate (7) (7 ') and the side plate (16).

The core plates (7) (7 ') and the side plates (16) were heated at 100 ° C. for 5 minutes to remove water in the flux composition.

The core plate (7) (7 ') and the side plate (16) are transported, and the corrugated fin (2), the refrigerant inlet pipe (14) and the refrigerant outlet pipe (15) are provided.
At the same time, a heat exchanger was assembled.

The assembled heat exchanger was heated at 150 ° C. for 5 minutes to thermally decompose the polymer compound in the flux composition.

The wax was heated at 600 ° C. for 5 minutes to melt and join.

[Step II (Conventional Method)] A predetermined amount of the flux composition was spray-coated on the core plate (7) (7 ') and the side plate (16).

The core plate (7) (7 ') and the side plate (16) were heated at 150 ° C. for 5 minutes to remove water in the flux composition and thermally decompose the high molecular compound.

The corrugated fins (2), the refrigerant inlet pipe (14) and the refrigerant outlet pipe (15) are conveyed by conveying the core plates (7) (7 ') and the side plates (16).
At the same time, a heat exchanger was assembled.

The solder was heated at 600 ° C. for 5 minutes to melt and join.

After brazing, the brazing property was evaluated based on the state of fillet formation, and the amount of flux residue dropped into the heat exchanger was evaluated by visual observation. Table 2 shows the evaluation results.

From the results in Tables 1 and 2, the brazing method of the present invention not only has good adhesion of the flux composition to be used, but also conveys in a state where only the moisture is removed and the flux is strongly adhered after application. By performing work such as assembling that may cause flux to fall off, and then thermally decomposing the resin binder, the flux can be reliably supplied to the joint without any excess or shortage when the wax is melted. It was confirmed that brazing could be achieved. Further, by adopting such a process, it was possible to prevent the residue of the falling flux from remaining inside the brazed product.

[0052]

As described above, the method for brazing an aluminum material according to the present invention comprises a fluoride-based flux;
A polymer compound containing 0 wt% and an alkylene oxide repeating unit having a number average molecular weight of 50,000 to 5,000,000;
Since a flux composition containing 5-70 wt% and the balance water is used, the flux strongly adheres to the aluminum material due to its viscosity. Further, since the dispersion medium is water and does not generate an unpleasant odor even when heated, it can be operated in a favorable environment and is safe for the human body. Furthermore, after applying such a flux composition to the bonding aluminum material, the application surface is heated to remove moisture, and then the application surface is heated to decompose and remove the polymer compound.
Since heating for brazing is performed, even if friction or vibration is applied to the aluminum material after heating to remove moisture and before heating to decompose the polymer compound, the flux does not fall off during the work, and the melting of the braze In some cases, the flux can be reliably present in the joint without excess or shortage, and good brazing can be achieved. In addition, since flux residues do not remain inside and outside the brazed product, problems such as poor coating, reduced corrosion resistance, and off-flavors caused by these are suppressed. This also eliminates the increase in passage resistance due to the above.

Further, in the brazing method, by performing the heating for removing the water at a temperature of less than 150 ° C., it is possible to reliably remove only the water and to leave the polymer compound as a binder. Efficient use of adhesive strength.

Further, by performing the heating for removing the polymer compound at 150 to 200 ° C. for 5 minutes or more, the polymer compound can be surely thermally decomposed. Therefore, high-temperature heating for melting the brazing can be performed in a state where the polymer compound is removed from the joint portion, and good brazing can be achieved.

[Brief description of the drawings]

FIG. 1 is a front view of a heat exchanger used as a specimen for a brazing test in an example.

FIG. 2 is a perspective view showing a part of the heat exchanger of FIG. 1 separately.

[Explanation of symbols]

 A: Heat exchanger 1: Tube element 2: Corrugated fin 7, 7 ': Core plate

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-7-155987 (JP, A) JP-A-4-147792 (JP, A) JP-A-4-84690 (JP, A) JP-A-9-99 174277 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B23K 1/19 B23K 1/00 B23K 35/363 C09J 171/00

Claims (3)

(57) [Claims] 1. A high molecular compound containing 5 to 30% by weight of a fluoride-based flux and an alkylene oxide repeating unit having a number average molecular weight of 50,000 to 5,000,000;
%, And after applying a flux composition composed of the balance water to an aluminum material for bonding, the application surface is heated to remove moisture, and then the application surface is heated to decompose and remove the polymer compound. After that, heating for brazing is carried out for brazing an aluminum material. 2. The method according to claim 1, wherein the heating for removing the moisture is performed at a temperature of less than 150 ° C. 3. The heating for removing the polymer compound,
The method for brazing an aluminum material according to claim 1, wherein the brazing is performed at 150 to 250 ° C. for 5 minutes or more.