JPH08187594A - Flux composition for brazing aluminum - Google Patents

Abstract

PURPOSE: To provide a flux compsn. suitable at the time of brazing of aluminum, a brazing filler metal and a brazing method. CONSTITUTION: This flux compsn. for brazing aluminum contains an org. high polymer of an average mol.wt. of 100000 to 5000000 consisting of a polyalkylene oxide as a main constituting component, an org. solvent and a fluoride based flux. This aluminum brazing paste contains this compsn. and aluminum alloy powder. This brazing method comprises using such paste.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flux composition used for joining aluminum members, a flux paste for aluminum brazing, and a brazing method thereof. As used in this specification, the term "aluminum member" includes structural members made of various aluminum alloys unless otherwise specified.

[0002]

2. Description of the Related Art In-furnace brazing has been remarkably developed in recent years as a brazing method for aluminum members.
This method is suitable for manufacturing aluminum heat exchangers for automobiles, and can braze hundreds of brazing points in one product in one step. A brazing sheet is used to braze the body of a heat exchanger as a conventional aluminum brazing material, and a brazing sheet using a brazing product is used to braze pipes. The powdered brazing paste is used as an auxiliary material for the brazing filler metal of the above and as a substitute for the brazing filler metal for brazing pipes. In any form of the aluminum brazing material, an aluminum-silicon alloy brazing material is used as the brazing material composition.

As one method of brazing aluminum members, a method of removing the aluminum oxide film existing on the surfaces of the joined parts by flux and brazing is used. In recent years, a non-corrosive, non-water-soluble aluminum fluoride-based flux has been developed as a flux material in place of the conventional chlorine-based flux (for example, JP-A-51-1).
No. 23749, JP-A-56-6797, JP-B-58-27037, JP-B-62-46280, JP-A-5-2434). Compared with conventional chlorine-based flux, this aluminum fluoride-based flux has almost no corrosiveness, water-solubility, and hygroscopicity, so immediately before use, an aqueous slurry containing aluminum alloy brazing powder and water is attached to the welded part. After that, water is evaporated and removed, and then a brazing method is used.

In addition, in the action of adhering the brazing material and the flux to the material to be brazed, water does not show sufficient adhering property, and the amount of flux flowing down after application is not small.
An extra coating is necessary considering the amount of runoff. Also,
In the conventional brazing method, water is used as a dispersion medium, and the flux used for brazing is dispersed in water as a dispersion medium at a predetermined concentration to form a suspension. When brazing by a person such as torch brazing, it is necessary to apply the flux in advance, but since the flux settles every time the application is performed and the flux is not uniform, stirring is required before the application, which is troublesome. This suspension is applied to the brazing part before brazing, but the flux should originally be applied only to the brazing part such as the contact part between the heat transfer tube and the fin, and may be applied to other parts. Not only is the flux wasted in vain, but the residue after brazing adheres to the surface of the fins, increasing airflow resistance, and if there is a large amount of residue, this residue may clog the fins. Will end up. However, when water is used as the dispersion medium, the viscosity of the flux suspension becomes extremely small (the fluidity becomes extremely good), and it is not possible to apply this suspension only to the brazing part. It will be difficult. For this reason, conventionally, not only the portion necessary for brazing but also the other portions are coated with the flux suspension by spraying, etc., and therefore the above-mentioned problems cannot be avoided after brazing. It was

In order to solve these drawbacks, resins added as a tackiness improver or the like of vehicle (a flux or a dispersion medium of flux and aluminum alloy brazing powder, which is a general term for resins and organic solvents) For example, the technology to add carboxymethyl cellulose, rosin resin, vinyl acetate resin, etc.) was developed, but inside the fillet due to decomposition gas or carbonization generated during the heating process until the brazing temperature (about 600 ° C) is reached. A defective appearance and a defective joint due to a black residue generated on the surface and a black residue generated on the surface are recognized. Further, a thermal decomposition product is generated and adheres to the aluminum brazing furnace.

As a solution to such a problem, there is known a method in which an organic resin which volatilizes rather than decomposes and carbonizes in the process of heating up to the brazing temperature is mixed as a vehicle with the brazing metal powder. As this type of resin, for example, JP-A-2-147193 discloses an acrylic resin, and JP-B-63-43200 discloses an ethylene oxide polymer, a polyacrylate polymer, a polymethacrylate polymer, and a polyacrylonitrile. Polymers, polyethylene glycol and its methyl ethers, and aliphatic hydrocarbon polymers are described, and JP-A-2-268 is also known.
Japanese Patent Publication 995 discloses polyisobutylene and polybutene.

Further, Japanese Patent Laid-Open No. 55-500263 and Japanese Patent Laid-Open No. 56-6797 disclose hydroxypropyl cellulose, glycerin, and polyalkoxyalkanols.

Further, JP-A-56-95489 discloses that
Regarding brazing of copper powder, it discloses that polyalkylene glycol having a molecular weight of 2,000 to 40,000 is used for the brazing. It is described that residual carbon is inevitable after firing when the molecular weight of polyalkylene glycol is 100,000 or more, which suggests that use of high molecular weight polyalkylene glycol is not preferable.

The above-mentioned Japanese Patent Publication No. 63-43200 discloses the use of ethylene oxide polymer, which is used only by using an anhydrous vehicle and an anhydrous flux, because it has a long shelf life. Since the flux uses a highly hygroscopic chloride together with an alkali metal fluoride, using this together with a hygroscopic ethylene oxide polymer causes a decrease in stability and brazing performance due to the reaction of the aluminum powder during storage of the paste, Further, there is a problem that a cleaning treatment must be performed after brazing in order to prevent corrosion of aluminum due to the chloride.

In the invention described in Japanese Patent Application Laid-Open No. 2-147193, since the acrylic resin generates toxic monomers having a strong irritating odor by thermal depolymerization, brazing in the atmosphere, for example, torch wax. At the time of attachment, there are concerns about the work environment. The polybutene and hydrocarbons described in JP-A-1-143996 and JP-A-2-268995 generate a large amount of black smoke during atmospheric brazing, particularly torch brazing, and therefore these are also concerned about the work environment.
In the brazing in the furnace, the above-mentioned Japanese Patent Laid-Open No. 1-143796.
Polybutene and hydrocarbons described in JP-A No. 2-268995 and JP-A No. 2-268995 require cleaning as the main tense of the furnace because the polyolefin generated by decomposition by heating accumulates on the furnace wall to some extent. When brazing in the atmosphere,
In particular, in torch brazing, black oil smoke is generated, which significantly deteriorates the working environment. This is also the case with high-frequency brazing because it produces a large amount of smoke.

[0011] For example, conventionally, CFC or the like has been used for cleaning due to safety of human body and fire, but since it cannot be used due to global environmental problems, dangerous work and further cost increase.

[0012]

DISCLOSURE OF THE INVENTION The present invention is for aluminum brazing in which aluminum is not brazed except for a required portion, a thermal decomposition residue is hardly generated, and there is no fear of deteriorating the working environment even in atmospheric brazing. Flux composition and brazing method.

[0013]

The present invention has a polyalkylene oxide as a main constituent and an average molecular weight of 100,000 to 50.
The present invention relates to a flux composition for aluminum brazing using a flux and a flux and a dispersion medium of an aluminum alloy brazing powder, and a brazing method thereof.

The organic polymer used in the present invention has polyalkylene oxide such as polyethylene oxide, polypropylene oxide and polybutylene oxide as a main constituent component in the molecule, and has an average molecular weight of 100,000 to 500.
It is a high molecular weight compound of 10,000, preferably 100,000 to 1,500,000. In the present invention, it is important to use a high molecular weight organic polymer.

If the molecular weight is less than 100,000, sufficient viscosity will not be obtained unless a large amount of the organic polymer is used in the compounding, and the viscosity of the paste will increase due to hydroxyl groups. On the other hand, if the molecular weight is too large, the spinnability becomes too strong, and the viscoelastic properties deteriorate. Polyalkylene oxide organic polymers with a molecular weight of 100,000 or more have low hygroscopicity,
Less deterioration of the composition than low molecular weight glycols.

The above organic polymer may be a homopolymer of the same alkylene oxide or a block or random copolymer of the different alkylene oxide as long as it is a high molecular weight compound. More preferred organic polymer is
A polyalkylene oxide compound obtained by addition-polymerizing a lower alkylene oxide such as ethylene oxide to an organic compound having two or more active hydrogen groups, and a compound thereof and a polyvalent carboxylic acid, its anhydride or its lower alkyl ester or diisocyanate. It is a high molecular weight compound obtained by reaction. In addition to a hydroxyl group, it has an alkoxy group, a carboxyl group, or an ester group at the terminal of the molecule, and has an ester bond or a urethane bond in the molecule in addition to an ether bond.

Organic compounds having two or more active hydrogens include ethylene glycol, propylene glycol,
Examples thereof include polyhydric alcohols such as 1,3-butylene glycol and hydrogenated bisphenols and polyhydric phenols such as bisphenol dihydroxypropyl ether. Further, as the polyvalent carboxylic acid, maleic acid, fumaric acid,
Examples thereof include succinic acid, gluconic acid, adipic acid, sebacic acid, isophthalic acid, terephthalic acid and trimellitic acid.

Regarding the aromatic carboxylic acid, generation of residual carbon was observed on the surface of the brazing material during the brazing process. The types of carboxylic acid and the amount of residual carbon were in the order of succinic acid <adipic acid <phthalic acid.

As the method for producing an organic polymer, not only general addition polymerization of alkylene oxide but also polymerization reaction using a Ziegler-Natta catalyst in a suitable organic solvent can be applied. The polyalkylene oxide produced by the polymerization reaction using the Ziegler-Natta catalyst is preferably a substance containing few metal impurities such as Ti, Al, Zn and Si, and is preferably 0.5% or less, more preferably 1000 ppm or less. This type of polymer is an odorless and nontoxic substance, is stable against oxygen, ozone, acid, alkali, ultraviolet rays, etc., and has a viscosity of 23 when dissolved in a solvent.
Since a liquid of 200 to 30,000 cps can be obtained at a temperature of ° C, the coating operation becomes easy. In the air, about 200-35
Since it decomposes completely and volatilizes at 0 ° C. and at about 300 to 400 ° C. in a nitrogen atmosphere, no carbonization residue occurs after brazing.

The organic solvent used in the present invention must be inert to the aluminum alloy braze and capable of dissolving high molecular weight polyalkylene oxides.
Moreover, it is desired that the product itself be safe and easy to handle, generate no harmful gas when the furnace is used, and have a good usability.

It is most important that the organic solvent does not absorb moisture or react. Further, since the composition has different usage conditions, there are various cases in which it is desired that the composition evaporate quickly, and it is preferable that the composition evaporate slowly. Therefore, a technique capable of providing an article suitable for the composition is desired. After the paste is applied, it flows over time due to heating and spreads out. In order to prevent this, it is effective to blend a low boiling point solvent. The boiling point of the paste-free paste solvent is 200 ° C. or lower, preferably 160 ° C. or lower, and particularly preferably 150 ° C. or lower. Further, since the polyalkylene glycol is soluble in water or a water-soluble solvent, it can be easily handled during use or after washing.

As the organic solvent having such characteristics,
Those having an alkylene group having 3 to 4 carbon atoms, polyglycols thereof, and monoethers thereof with lower alcohols (C1 to C4) are preferable. Particularly, alkylene glycols are ethers of C1-4 alcohols having a propylene residue, such as dipropylene glycol, tripropylene glycol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monoisopropyl ether. , Propylene glycol monobutyl ether / propylene glycol monoisobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether,
Dipropylene glycol monobutyl ether and dipropylene glycol monoisobutyl ether can be mentioned. The composition is selected from the above and / or 1,4-
It contains at least one solvent selected from dioxane. Ethylene solvents are inferior in terms of paste viscosity stability, toxicity, and safety and hygiene. Other than these, dibutylene glycol and the like are preferable.

Examples of suitable low boiling point solvents include 1,4-dioxane and dipropyl ether. These are volatile at room temperature and highly flammable, so caution is required when using them. The choice of solvent used in the present invention is of paramount importance to the technology of the present invention.

These solvents dissolve polyalkylene oxides well, have low hygroscopicity, and have low reactivity and high stability over time even when aluminum powder is mixed. The vehicle obtained by dissolving the polyalkylene oxides has good coatability and quick recovery of viscosity after coating, and thus has good workability and stability. It also evaporates polyalkylene oxides well when brazing in the atmosphere, does not generate residual carbon in the brazing part, does not generate black smoke, maintains a clean working environment, and is good even when mixed with aluminum powder. Shows excellent storability. Needless to say, brazing in the furnace has good brazing property.

As the flux that can be used in the present invention, aluminum fluoride series is preferable. The aluminum fluoride system referred to here is a flux containing fluorine and aluminum, and is aluminum fluoride potassium flux, that is, AlF ₉ -KF, KAlF ₄ -K ₅ AlF ₆ ,
K ₃ AlF _6, KAlF has _{4, KF-AlF 3 -Al 2} O 3 or the like, other CsxAlyF ₂ etc. can also be exemplified. Aluminum potassium fluoride flux is particularly preferable.

The amount of the above-mentioned flux compounded is 10 to 75% by weight based on the total weight of the flux composition. The spread and flow range of the flux can be changed by adjusting the amount of vehicle and the amount of flux. It is the oxygen content of the aluminum brazing material that affects the amount of flux, but since the oxygen content will vary depending on the construction method and the shape of the aluminum brazing material, it will be adequately addressed within the scope of the present invention by blending in timely consideration. it can. When the amount of flux is less than 10% by weight, the amount of flux applied is small, which may cause brazing failure. When the amount of the flux is more than 75 parts by weight, the spread and the flow are improved, but a large amount of white residue and black spots are generated on the surface of the fillet, which leads to a poor product appearance. In the case of the flux brazing as described above, it is also very useful to form a paste by mixing the aluminum alloy brazing powder and the flux with the vehicle within the scope of the claims of the present invention. This is because the aluminum alloy brazing powder mixed in advance has the function of an auxiliary agent for improving the flowability and the gap filling property of the brazing material set in the brazing part.

When copper, silicon or the like is contained as a component of the material to be brazed, the melting point of the material to be brazed becomes low, so that it is necessary to lower the working temperature of the flux. It is effective to contain Cs, Sr, Ba, Zn, and Cu in order to lower the action temperature of the flux, and examples of the method include single, mixed, and reaction products such as fluoride oxides. Instead, it is included in the technical scope of the present invention.

The aluminum brazing flux composition for the torch needs to use a larger amount of flux than the aluminum brazing flux composition in the furnace. Further, when a chloride-based flux that has been conventionally used for brazing in a furnace is used in a composition, the hygroscopicity of the chloride-based flux lowers the storage stability of the composition. Further, when a chloride-based flux is used, it will corrode unless the brazed portion is cleaned after brazing. Therefore, the aluminum brazing composition is particularly preferably a fluoride-based flux and has almost no hygroscopicity, so that no washing step is required. This is as described above.

Further, the fluoride type flux can be made into a fine powder. By using a large amount of finely divided fluoride-based flux, the viscosity of the composition can be increased, and a brazing composition having a desired viscosity can be obtained without using a large amount of organic polymer or thickener. it can.

The amount of components in the vehicle is 0.5 for the organic polymer.
˜70 wt%, preferably 1 to 25 wt%, more preferably 2 to 10 wt%.

The organic solvent content is 30 to 99.5% by weight, preferably 75 to 99.5% by weight, more preferably 9% by weight.
It is 0 to 99.0% by weight. Regarding the amount of the fluoride-based flux, the optimum brazing can be obtained within the scope of the present invention by changing the blending amount in a timely manner depending on the intended use.

Although not more than 10 parts by weight of aluminum alloy brazing powder is blended with the flux composition for aluminum brazing of the present invention, good brazing properties can be obtained without blending the brazing powder. A small amount of aluminum alloy brazing powder serves as an auxiliary agent for improving brazeability.
In particular, when the amount of brazing filler metal set in the brazing portion is small in advance or when the gap in the brazing portion is large, the amount of brazing filler metal and the powdered brazing filler are increased by blending this composition as described above. Since the material flows to the lacking part and the lack of brazing is eliminated, reliable and good brazing can be obtained. In particular, when brazing brazing material with a brazing material such as brazing sheet, the brazing material may not be fully supplied to the brazing part. It is extremely effective. When the amount of the aluminum alloy brazing powder is more than 10 parts by weight, the amount of the brazing material supplied to the brazing part becomes too large, and the amount of the flux to be compounded becomes insufficient, so that good brazing property cannot be obtained. is there.

As the aluminum alloy powder which can be blended in the flux composition for aluminum brazing of the present invention, an aluminum alloy having a melting point lower than that of the aluminum members to be joined is used. Among them, the aluminum-silicon alloy system is preferable, and the aluminum-silicon (7 to 15%) system, the aluminum-silicon (7 to 15%)-X system (X is at least one of copper, magnesium and zinc). ),
Further, those containing bismuth, tin, barium or the like as the third additive element can be exemplified.

The average particle size of the powder is 10 to 500 μm, preferably 40 to 150 μm, and if it is less than 10 μm, the specific surface area of the powder becomes excessively large, so that the content of oxides becomes large and the powders are sufficiently fused to each other. It becomes difficult to integrate. On the other hand, if it exceeds 500 μm, the number of powders per weight of the aluminum brazing material decreases, and the gap between the powders becomes too large, which makes it difficult to perform precise brazing. The shape of the powder does not matter. The oxygen content of the aluminum alloy brazing powder is preferably 0.2% by weight or less, more preferably 0.1% by weight or less.

In order to adjust the coating workability of the flux composition for aluminum brazing according to the present invention, an organic viscosity modifier or a diluting solvent can be used immediately before use. The viscosity may be adjusted by using a viscosity modifier, but the amount is 10% by weight or less, preferably 5% by weight or less.
Examples of preferable viscosity modifiers include 12-hydroxystearic acid, wax, synthetic wax, paraffin wax, microcrystalline wax, polyethylene wax, hardened oil, hardened castor oil, fatty acid amide and polyamide, but especially polyethylene wax, hardened wax. Castor oil is preferred. The viscosity of the flux composition for aluminum brazing according to the present invention may be appropriately selected according to the operation method of the paste.

In the method of the present invention, in the conventional polymer, the vehicle component adheres to the vicinity as a water-insoluble component, but since the product of the present invention is water-soluble, safe and inexpensive maintenance using water can be performed, and soot, malodor, and residual carbon can also be obtained. In addition, the method is excellent in coating property and does not deteriorate during storage. Further, as described above, water has a problem in coating workability, and water becomes a problem during brazing (deterioration of brazing atmosphere due to water vapor). It takes a lot of work because it puts the furnace for brazing and brazing. Since the vehicle used in the present invention is sufficiently decomposed and volatilized during the temperature rising process in the brazing furnace and does not deteriorate the brazing atmosphere, it is not necessary to provide a pre-drying step. The composition of the present invention may optionally further contain conventional additives in addition to the above-mentioned components.

The present invention further relates to a method for brazing an aluminum member using the flux composition for aluminum brazing.

In the brazing method using the flux composition for aluminum brazing of the present invention, an appropriate amount can be uniformly applied to a predetermined brazing portion, and the flux does not drop during application. Further, as described above, by using the aluminum alloy brazing powder, it is industrially very useful as a construction method to use this composition for brazing in which the brazing material is insufficient.

The present invention will be described below with reference to examples.

EXAMPLES AND COMPARATIVE EXAMPLES The flux compositions for aluminum brazing of the present invention were prepared according to the formulations shown in Table 1.

[0040]

[Table 1]

* 1 160mg brazing filler metal pellet * 2 "NOCOLOK" aluminum fluoride flux
Alkyan * 3 12% Si residual Al alloy powder (average particle size 70 μm,
Oxygen content 0.02%) 100 parts by weight * 4 20% PO remaining EO Random copolymer
Molecular weight 400,000 (PO is propylene oxide, EO is ethylene oxide) * 5 EO and PO phthalate ester polymer, molecular weight 100,000 to 150,000 * 6 EO and PO urethane polymer, molecular weight 100,000 to
150,000 * 7 Polymethylmethacrylate

Example 1 and Comparative Example 1 JIS 3003 aluminum plate (thickness 2 mm)
IS4343 aluminum brazing alloy plate with a clad rate of 1
It was clad at 0%. The aluminum brazing composition was used in an amount of 100 mg with respect to the clad plate (15 mm × 40 mm).

Each of the samples of Examples 2 and 3 and Comparative Examples 2 to 5 was treated with aluminum (test plate JIS3003) 1
(2 mm x 15 mm x 30 mm) and 2 (2 mm x 10 mm x 24 m
1) (top view) and FIG. 2 (front view) using m), 100 mg of the brazing composition for aluminum brazing and 160 mg of brazing filler metal are placed at predetermined positions in the central portion on one side of the T joint prepared as shown in FIG. Brazing was performed (600 ° C., 5 minutes).

* Evaluation method * Preservability (separation of composition after 1 month at 25 ° C) ○: No separation △: Vehicle is bleeding on the surface ×: Separation (flux etc. is settled) -Brazing property (fillet formation rate) O: Fillet formation rate 100% △: Fillet formation rate over 60 and less than 100% X: Fillet formation rate 60% or less

・ Combustibility of vehicle (combustion condition in the atmosphere) ○: Soot is not given (no problem in work) △: Soot is given (work is disturbed) ・ Washability After passing through a cooling pipe, the detergency of the condensed components against water was investigated. ○: Melted ×: Not melted ・ Coating workability ○: A predetermined amount can be applied to a predetermined brazed part △: Dripping from the predetermined brazed part spreads ×: Can not be applied as desired ・ Decomposition gas odor ○: Not particularly worrisome x: Smell of specificity-Fillet formation rate O: Fillet formation rate of 100% △: Fillet formation rate of more than 60% and less than 100% x: Fillet formation rate of 60% or less

* Brazing method * ・ In furnace: N ₂ gas (purity 99.999%) 6
Hold at 00 ° C (after melting of brazing material) for 5 minutes, and braze. -Torch: Brazing with butane gas flame in the atmosphere.

[0047]

INDUSTRIAL APPLICABILITY The present invention exhibits excellent brazing properties, has good decomposability during brazing, and does not generate soot or peculiar odor. Also, good brazing can be performed without generation of decomposition residues.

[Brief description of drawings]

FIG. 1 is a top view of a T joint used for evaluating the properties of an aluminum brazing paste.

FIG. 2 is a front view of a T joint.

[Explanation of symbols]

 1 Aluminum test plate 2 Aluminum test plate 3 Brazing material

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Tatsuyuki Ujie 3-6-8, Kutaro-cho, Chuo-ku, Osaka-shi, Osaka Toyo Aluminum Co., Ltd.

Claims (2)

[Claims] 1. (A) 0.5 to 70% by weight of an organic polymer containing polyalkylene oxide as a main constituent and having an average molecular weight of 100,000 to 5,000,000; (B) 30 to 99.5% by weight of an organic solvent; Flux composition for aluminum brazing containing 25 to 90% by weight of a vehicle comprising A) and (B) and 10 to 75% by weight of a fluoride flux, and the composition 100
Aluminum alloy brazing powder is further added to 10 parts by weight.
A flux composition for aluminum brazing, which comprises not more than 1 part by weight. 2. The aluminum brazing flux composition according to claim 1 and the aluminum alloy brazing material are interposed between the aluminum materials to be brazed at the positions to be brazed and heated to a temperature above the melting point of the brazing alloy. A method for brazing an aluminum member, comprising: