JP3143076B2 - Flux composition for brazing aluminum material - 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 composition for brazing aluminum materials, and more particularly to a flux composition used for brazing members made of aluminum or an aluminum alloy in the manufacture of a heat exchanger.

[0002]

BACKGROUND OF THE INVENTION In recent years, furnace brazing has been remarkably developed as a method of brazing aluminum members.
This method is suitable for manufacturing aluminum heat exchangers for automobiles, and can perform several hundreds of brazings in one product at a time.

[0003] A brazing sheet is used for brazing a heat exchanger body as a conventional aluminum brazing material. A brazing braid using a brazing molded product of pipes is used. Powdered brazing paste is used as an auxiliary material for brazing materials and as a substitute for brazing pipes. In any of the forms of the aluminum brazing material, an aluminum-silicon alloy-based brazing material is used as the brazing material composition.

As one method of brazing an aluminum member, a method of brazing by removing an aluminum oxide film interposed on the surface of a portion to be joined by using a flux is used. In recent years, a non-corrosive, water-insoluble aluminum fluoride-based flux has been developed as a flux material instead of the conventional chlorine-based flux.

[0005] This aluminum fluoride-based flux is
Compared to conventional chlorine-based flux, it has almost no corrosiveness, water solubility, and hygroscopicity. Therefore, immediately before use, an aqueous slurry dispersed in water together with aluminum alloy brazing powder is attached to the part to be joined, and water is removed by evaporation. After that, a method of brazing is performed.

When the above-mentioned aqueous brazing material or flux is applied to an aluminum member, water does not show sufficient adhesion, so that the amount of flux that flows down after application is not small. Therefore, the amount of application must be increased, which wastes. In addition, since the flux composition that has flowed adheres to the vicinity of the brazing portion, the appearance deteriorates, and after brazing, a residue adheres to, for example, the surface of a fin of a heat exchanger to increase airflow resistance, When the number is extremely large, there is a problem that the fins are clogged.

[0007] In order to solve these drawbacks, a tackifier for a vehicle (a dispersion medium of flux or a flux and an aluminum alloy brazing powder, which is a collective term of resins and organic solvents) using an organic solvent as a dispersion medium, etc. As resins (for example, carboxymethylcellulose, rosin resin,
A technique of adding a vinyl acetate resin) has been developed. For example, in the "brazing method" of JP-A-7-185796, polyvinyl alcohol is proposed as the above resin.

[0008] However, such a flux composition has a decomposition gas generated in a heating process until reaching a brazing temperature (about 600 ° C), a void generated in the fillet due to carbonization, and a black color generated on the surface. There was a problem that poor appearance or poor bonding due to the residue was observed. Further, there is a disadvantage that a thermal decomposition product is generated and adheres to the aluminum brazing furnace.

Therefore, a flux composition using a resin which does not easily generate a thermal decomposition residue without polluting the periphery of the brazing portion has been proposed in Japanese Patent Application Laid-Open No. 8-187594, "Flux composition for aluminum brazing". Was. That is, in order to improve fluidity, an organic solvent such as 1,4-dioxane or dipropyl ether is used as a dispersion medium, and a resin containing polyalkylene oxide as a main component, which is unlikely to generate a thermal decomposition residue, is dissolved to improve fluidity. It is improved to improve the adhesion.

[0010]

However, the organic solvent used in the flux composition disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 8-187594 has a high volatility and a high flammability, so that it needs to be handled with care. , Especially 1,4
-Dioxane is toxic, so there was a problem in health and safety.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has as its object to improve the adhesion of a flux applied to a member to be brazed and to eliminate the presence of thermal decomposition residues during brazing. An object of the present invention is to provide a flux composition for aluminum brazing.

[0012]

In order to achieve the above-mentioned object, a flux composition for brazing an aluminum material according to the present invention comprises a polymer comprising a repeating unit of alkylene oxide having a number average molecular weight of 50,000 to 2,000,000. 0.5 to 10 parts by weight of the compound and 5 to 3 parts of the fluoride flux
0 parts by weight and 60 to 94.5 parts by weight of water.

As described above, since water is used as the dispersion medium of the flux and a resin that decomposes and volatilizes at 140 ° C. to 200 ° C. is used, simple preliminary heating is performed in the pre-brazing step, so that the resin The components can be removed, and only the flux effective for brazing can be supplied to the aluminum material. Therefore, there is no possibility that the furnace will be contaminated by the decomposition residue of the resin component and the resulting brazing failure will not occur.

Further, the flux composition for brazing an aluminum material according to the present invention comprises a nonionic surfactant in an amount of 0.1 to 1%.
Contains 3 to 5 parts by weight.

[0015] The nonionic surfactant has a high affinity for the flux, whereby the flux can be stably dispersed in the composition. Therefore, the stability over time of the flux composition is improved.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below. In the present embodiment, “aluminum material”
The term "includes" structural members made of various aluminum alloys in addition to pure aluminum unless otherwise specified.

<Polymer Compound> The polymer compound used in the present invention has an alkylene oxide repeating unit such as ethylene oxide and propylene oxide and has a number average molecular weight of 50,000 to 2,000,000, preferably 50,000 to 2,000,000.
One million high molecular compounds.

If the average molecular weight is less than 50,000, sufficient viscosity cannot be obtained unless a large amount of a high molecular compound is blended, resulting in poor economic efficiency. On the other hand, when the average molecular weight exceeds 2,000,000, the spinnability becomes too strong, and the viscoelastic properties deteriorate.

The polymer compound according to the present invention may be a homopolymer of an alkylene oxide, or may be a copolymer with a different alkylene oxide or another compound. Further, the above-mentioned alkylene oxide may be linear or branched.

When the average molecular weight is less than 50,000, the thermal decomposability is poor (the thermal decomposition onset temperature is the same as that of the high molecular compound having a molecular weight of 50,000 to 2,000,000, but it takes time to completely decompose it. ), It is easy to generate thermal decomposition residue after brazing.
Further, a block or random copolymer of a different alkylene oxide has better thermal decomposability than a homopolymer of the same type of alkylene oxide, and is more advantageous for blackening resistance due to a thermal decomposition residue after brazing. (The EO-PO random copolymer has better thermal decomposability than the EO homopolymer.)

The polymer compound is more preferably 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 polyvalent carboxylic acid, It is a high molecular weight compound obtained by reacting the anhydride or the lower alkyl ester or diisocyanate. The molecular terminal 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 hydrogens include polyhydric alcohols such as ethylene glycol, propylene glycol, 1,3-butylene glycol, glycerin, trimethylolpropane and pentaerythritol, hydrogenated bisphenol and bisphenol dihydroxypropyl. Examples are polyhydric phenols such as ethers. Further, as the polycarboxylic acid, maleic acid,
Examples thereof include fumaric acid, succinic acid, gluconic acid, adipic acid, sebacic acid, isophthalic acid, terephthalic acid, and trimellitic acid.

The flux composition of the present invention contains 0.5 to 10 parts by weight of the polymer compound. More preferably, the content is 1 to 5 parts by weight. When the content of the polymer compound is less than 0.5 part by weight, sufficient viscosity cannot be obtained, so that the amount of adhered flux is reduced and there is a problem that poor brazing occurs. On the other hand, if the content exceeds 10 parts by weight, the viscosity becomes unnecessarily high, so that the adhesion amount of the resin increases, and a thermal decomposition residue is generated during brazing. Furthermore, it is not economical because excessive flux adheres.

<Dispersion Medium> In the present invention, water is used as a dispersion medium. Therefore, since no organic solvent is used, there is no danger of ignition or explosion due to the volatilization of the solvent, which is safe, and the harmful solvent is not diffused during the operation, so that the sanitary aspect is improved.

<Flux> The flux used in the present invention is preferably a fluoride-based flux. As the fluoride-based flux, potassium aluminum fluoride flux, that is, AlF ₃ -KF, KAlF ₄ -K ₃ AlF ₆ , K ₃ AlF
_6, there is _{KAlF 4, KF-AlF 3 -Al} 2 O 3 or the like,
Other examples include Cs _x Al _y F _Z.

The flux composition of the present invention contains 5 to 30 parts by weight of the fluoride-based flux, and more preferably 5 to 20 parts by weight of the flux. If the content is less than 5 parts by weight, the amount of flux to be applied is small, which may cause poor brazing. On the other hand, when the content exceeds 30 parts by weight, the flux improves the spread and flow of the brazing material, but leads to poor appearance of the product such as generation of a large amount of white residue on the fillet surface.

<Nonionic surfactant> Examples of the nonionic surfactant used in the present invention include polyoxyethylene glycol, polyoxyethylene polyoxypropylene glycol, polyoxyethylene alkylphenyl ether, polyoxyethylene alkyl ether, glycerin fatty acid esters, sorbitan fatty acid esters, pentaerythritol fatty acid esters, polyoxyethylene glycerin fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene pentaerythritol fatty acid esters, polyoxyethylene alkyl amino ether, ethylenediamine polyoxyethylene polyoxypropylene Glycol is used.

In the flux composition of the present invention, nonionic
System boundary surface active agent is contained 0.03 to 5 parts by weight. More preferably, the content is 0.04 to 1 part by weight. If the content of the nonionic surfactant is less than 0.03, the hula
Flux dispersibility is reduced and flux is easily separated.
You. On the other hand, when the content is more than 5 parts by weight, the dispersibility of the flux is improved, but there is a problem that a non-ionic surfactant generates a heat dispersion residue during brazing.

<Flux / Polymer Compound Ratio> As described above, the flux composition of the present invention contains 0.5 to 10 parts by weight of a polymer compound and 5 to 30 parts by weight of a fluoride-based flux. I do. That is, the weight ratio of flux / polymer compound is 0.5 to 60. A more preferred weight ratio is from 1 to 20. When the weight ratio is less than 0.5, sufficient adhesion can be obtained, but the amount of the polymer compound for maintaining the flux is too large, and a thermal decomposition residue is generated when brazing is performed. On the other hand, when the weight ratio is 60
If it exceeds, the amount of the compound required for maintaining the flux will be reduced, and the disadvantage that the adhesion will be reduced will occur.

<Ratio of flux / nonionic surfactant> The weight ratio of flux / nonionic surfactant is 1
, And more preferably a weight ratio of 5 to 500.
It is. When the weight ratio is less than 1, the dispersibility of the flux is improved, but when brazing is performed, a thermal decomposition residue due to a nonionic surfactant is generated (the polymer compound thermally decomposes at 140 to 200 ° C.). Whereas surfactants thermally decompose at 200-250 ° C). On the other hand, when the above weight ratio exceeds 1000, the dispersibility of the flux is reduced, and there is a disadvantage that the flux is easily separated.

<Viscosity of Flux Composition> The flux composition of the present invention preferably has a viscosity of 150 cps to 500 cps at room temperature (23 ° C.). 1
If it is less than 50 cps, the amount of adhered flux will be reduced, resulting in poor brazing. If it exceeds 500 cps,
When the brazing is performed, a white residue of the flux is generated because the flux adheres more than necessary. <Brazing method> brazing method, the joined part of the above flux composition aluminum material manufactured by clad plate (e.g. an aluminum alloy material of JIS4343 material on both surfaces of the core material JIS3003 material was clad with the cladding 10%) Suitable amount (about 2 g / m ² as potassium aluminum fluoride flux)
Apply and dry with water. Next, the clad plate to which the flux composition is attached is combined with a target structure, and the assembled structure is heated and maintained at 600 ° C. for several minutes in a nitrogen atmosphere to perform brazing.

Further, another preferred embodiment of the present invention will be described below.

1. The polymer compound used in the present invention has an alkylene oxide repeating unit such as ethylene oxide and propylene oxide.

2. The polymer compound is preferably a polymer compound having a number average molecular weight of 50,000 to 1,000,000.

3. The polymer compound used in the present invention may be a homopolymer of an alkylene oxide or a copolymer of a different alkylene oxide.

4. The alkylene oxide may be linear or branched.

5. The fluoride-based flux used in the present invention is a potassium aluminum fluoride flux, that is, AlF ₃ -KF, KAlF ₄ -K ₃ AlF ₆ , K ₃ AlF.
_{6, KAlF 4, KF-AlF} 3 -Al 2 O 3, Cs x A
l _y F _Z.

6. The weight ratio of flux / polymer compound is 0.5 to 60 (preferably 1 to 20).

7. The weight ratio of flux / nonionic surfactant is 1 to 1000 (preferably 5 to 500).

[0040]

Next, the present invention will be described in detail with reference to examples and comparative examples. Note that the present invention is not limited by these examples.

Examples 1 to 4 and Comparative Examples 1 to 4 (1) Preparation of Flux Composition According to the formulation shown in Table 1, flux compositions used in Examples and Comparative Examples were prepared.

[0042]

[Table 1] (2) Evaluation test An appropriate amount of a fluoride-based flux of about 2 g / m ^{2 is} applied to a portion to be joined of an aluminum alloy material in which JIS4343 material is clad on both sides of a core material JIS3003 material at a cladding ratio of 10%, and moisture is dried. Next, the clad plate to which the flux composition was adhered was combined with a target structure, and the assembled structure was heated and maintained at 600 ° C. for several minutes in a nitrogen atmosphere to perform brazing.

(3) Evaluation method (a) Adhesion of flux ○: flux does not fall off even when rubbed with hand △: flux does not fall off when touched by hand, but falls off when rubbed ×: flux when touched by hand (B) Brazeability (fillet formation rate) ○: Fillet formation rate 100% △: Fillet formation rate 60% or more and less than 100% ×: Fillet formation rate less than 60% (c) Vehicle flammability (brazing) ×: No thermal decomposition residue is generated. ○: Thermal decomposition residue is generated. (D) Coating workability. ○: A predetermined amount of coating can be applied to a predetermined brazing part. △: Anybody from a predetermined brazing part. ×: Unable to apply as expected (e) Odor during coating work ○: Not particularly anxious ×: Specific odor (f) Dispersibility of flux (flush after standing at room temperature for one day) Box of separation) ○: × flux does not separate: flux based on the evaluation method described above for separating were evaluated examples and comparative examples. Table 2 shows the results.

[0044]

[Table 2] From these results, according to the flux composition of the present example, the adhesion of the flux applied to the member to be brazed is improved, and brazing without thermal decomposition residue when brazing is performed. It turns out that you can.

[0045]

As described above, according to the flux composition for brazing an aluminum material of the present invention, the adhesion of the flux applied to the member to be brazed is improved, and the heat during brazing is improved. Brazing without decomposition residue can be performed.

Further, by adding a nonionic surfactant to the flux composition, the dispersibility of the flux is improved.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Atsuhiko Tonaka 4-1-1-15 Minamishinagawa, Shinagawa-ku, Tokyo Nihon Paint Co., Ltd. Tokyo Office (72) Inventor Kiyotada Yasuhara 4-chome Minamishinagawa, Shinagawa-ku, Tokyo No. 1-15 Nihon Paint Co., Ltd. Tokyo Office (72) Inventor Hiroyuki Nojiri 4-1-1 Minami Shinagawa, Shinagawa-ku, Tokyo Nihon Paint Co., Ltd. Tokyo Office (72) Inventor Katsuyoshi Yamazoe Shinagawa-ku, Tokyo 4-1-1-15 Minamishinagawa Nihon Paint Co., Ltd. Tokyo Office (56) References JP-A-9-174277 (JP, A) JP-A-9-29487 (JP, A) JP-A-7-1555987 ( JP, A) JP-A-6-285682 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B23K 35/363

Claims (3)

(57) [Claims] 1. A polymer compound containing an alkylene oxide repeating unit having a number average molecular weight of 50,000 to 2,000,000, 0.5 to 10 parts by weight, a fluoride flux of 5 to 30 parts by weight, and water of 60 to 60 parts by weight. 94.5 parts by weight of the flux composition for brazing aluminum material. 2. A nonionic surfactant containing 0.03
The flux composition for brazing an aluminum material according to claim 1, wherein the flux composition comprises up to 5 parts by weight. 3. The flux composition for brazing aluminum material according to claim 2, wherein the weight ratio of the flux to the nonionic surfactant is 1 to 1000.