JP3438922B2 - Aluminum brazing paste for brazing in furnace - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum brazing paste for joining aluminum members in an inert atmosphere. As used herein, the term "aluminum" includes various aluminum alloys unless otherwise noted.

[0002]

2. Description of the Related Art As one method for brazing aluminum members, there is used a method in which an aluminum oxide coating present on the surfaces of the parts to be joined is removed with a flux using an aluminum brazing paste containing a flux to perform brazing. ing. In this case, in the temperature increasing process until the resins (eg, carboxymethyl cellulose, rosin resin, vinyl acetate resin, etc.) added as the tackiness improver of the binder component reach the brazing temperature (about 600 ° C.) Voids generated inside the fillet due to the generated decomposed gas and carbonization, appearance defects due to black residue generated on the surface, and joint defects are recognized. In addition, the production of flammable pyrolysates poses a problem such as the occurrence of fire hazards in aluminum brazing furnaces and performance degradation.

As a solution to such a problem, a method is known in which, in the process of raising the temperature to the brazing temperature, an organic resin that volatilizes rather than decomposes and carbonizes is blended as a vehicle or a binder into the brazing metal powder. There is. As this type of resin, for example, an acrylic resin is disclosed in JP-A-2-147193, and an ethylene oxide polymer, a polyacrylate polymer, a polymethacrylate polymer, a polyacrylonitrile polymer is disclosed in JP-B-63-43200. , Polyethylene glycol and methyl ethers thereof, and aliphatic hydrocarbon polymers are disclosed, and JP-A-2-268995 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 describes an aqueous brazing paste containing copper powder, and the brazing paste has a molecular weight of 2,000 to 40,
It discloses that 000 polyalkylene glycols are used. 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 the use of high molecular weight polyalkylene glycol is not preferable.

In the invention described in Japanese Patent Laid-Open No. 2-147193, the acrylic resin generates toxic monomers having a strong pungent odor due to thermal depolymerization, which is an environmental problem. No. Sho 63-4320
No. 0 discloses the use of ethylene oxide polymer, which only has a long shelf life with anhydrous vehicle and anhydrous flux, the flux used is with the alkali metal fluoride. Since a hygroscopic chloride is used in combination, when the hygroscopic ethylene oxide polymer is used in combination with the paste, the aluminum powder reacts with the paste during storage to cause deterioration in stability and brazing performance. There is a problem that a cleaning process must be performed in order to prevent corrosion of aluminum due to chloride.

Further, in the polybutene and the hydrocarbon described in JP-A-2-268995, the polyolefin generated by decomposition by heating accumulates in the furnace and causes pollution. Published Patent No. 55-500263 and Japanese Patent Laid-Open No. 56-679.
The hydroxypropyl cellulose and the like disclosed in Japanese Patent No. 7 have a drawback that they are carbonized by heating and generate voids. In particular, cellulosic resins and many polymers have residual carbon when heated, and the metal brazing powder is not sufficiently melted, resulting in defects such as metal residues, offensive odor, and soot.

Many of the above polymers are water-insoluble, and the storage stability of the metal brazing paste is good. But,
Many of the above polymers produce a variety of water-insoluble decomposition products on heating brazing in a furnace.

These products tend to adhere to the cold parts of the brazing furnace and accumulate over time. These contaminants are flammable and therefore a fire hazard. For the above reasons, the industrial brazing furnace is costly for cleaning and replacement.In particular, since cleaning CFCs cannot be used recently, there is a risk of using a flammable solvent and an increase in cost due to expensive equipment investment. There is.

On the other hand, as the aluminum brazing flux, a fluorine-based flux has been proposed in order to improve the above-mentioned drawbacks of the chloride-based flux (for example,
JP-A-51-123749, JP-B-58-270
37 and Japanese Patent Publication No. 62-46280).

However, in the inventions described in these publications, an aqueous slurry in which a water-insoluble fluorine-based flux is dispersed in water together with the brazing metal powder is attached to the jointed portion to remove water by evaporation. Later brazing requires an additional heating step to evaporate the water. Also, due to the water remaining in the paste,
There is a problem that viscosity change with time tends to occur. Also, when using metal powder with a very large surface area or when using powder with a large amount of oxide, the amount of flux used must be large, resulting in environmental pollution and corrosion of peripheral equipment. was there.

[0012]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems associated with the conventional method of brazing aluminum members in a furnace using brazing metal powder in the furnace, resulting in poor appearance and poor joining at the joint. In addition, it does not cause corrosion over time, does not generate a toxic gas that is highly irritating and poses a problem in work hygiene, and has little furnace contamination. Even if contamination occurs, it can be washed with safe and inexpensive water, and paste Shows a good storage stability, and further, an aluminum brazing paste that enables excellent brazing joining of aluminum parts with a minimum required amount of flux without requiring an additional heating step for brazing. It was made to provide.

[0013]

That is, according to the present invention, 100 parts by weight of an aluminum alloy powder having an average particle size of 10 to 500 μm, 0.5 to 15 parts by weight of an aluminum fluoride-based flux, and polyalkylene oxide as main constituent components. Organic polymer binder with an average molecular weight of 100,000-5,000,000 0.5
The present invention relates to an aluminum brazing paste for brazing an aluminum member containing 10 to 10 parts by weight and 30 to 150 parts by weight of an organic solvent.

The composition of the aluminum alloy brazing powder used in the present invention may be any aluminum alloy having a melting point lower than that of the aluminum members to be joined. For example,
Aluminum-silicon (5 to 15%) system, aluminum-silicon (5 to 15%)-X system (X contains at least one of copper, magnesium and zinc, and bismuth, tin, barium as a third additive element) The aluminum-copper alloy powder may be used, and the aluminum alloy brazing powder may be mixed with zinc powder, tin powder, barium powder, or the like.

The average grain size of the alloy powder is 10 to 500 μm.
m, preferably 40 to 150 μm, and when it is less than 10 μm, the specific surface area of the powder becomes excessively large and the amount of the oxide film increases, so that the powder particles are sufficiently fused and integrated with each other, which makes it difficult. On the other hand, when it exceeds 500 μm, not only the powder is difficult to disperse and suspend in the paste, but also the gaps between the powders become too large, which makes it difficult to perform a precise brazing.

The oxygen content of the aluminum alloy powder is preferably 0.2% by weight or less, more preferably 0.1% by weight.
It is the following. When the content is more than 0.2% by weight, the oxide film becomes thick, and in the case of aluminum, the oxide film is strong, so that the flux required to destroy the oxide film is 15
It must be added in an amount of at least part by weight. However, if 15 parts by weight or more of flux is added, the external appearance of the brazing becomes dirty due to flux residue and the like, which is inconvenient when the external appearance is left as it is. The shape of the aluminum alloy powder is not particularly limited, and as such metal powder, various shapes such as needle shape, plate shape, flat shape, granular shape, scale shape, and flake shape can be used. For example, a spherical or irregularly-shaped atomized Al alloy powder produced by atomizing in a non-oxidizing atmosphere is exemplified. Depending on the particle size and shape of the metal powder and the properties of the surface oxide film, if the oxygen content exceeds 0.2%, the surface oxide film does not break and does not melt and integrate even if it is suitable for the brazing temperature. In such a case, the amount of flux used should be 1
If the amount is more than 5 parts by weight, brazing itself is possible, but a large amount of white residue and black spots are generated in the brazing part, and the brazing furnace is contaminated and corrosion problems occur.

The aluminum fluoride type flux used in the present invention is used. Specifically, AlF ₃ -KF, KA
_{lF 4 -K 3 AlF 6, K} 3 AlF 6, KAlF 4, KF-AlF 3
-Al ₂ O _3, a flux containing CsxAlyFz the like. As the aluminum fluoride-based flux, a commercially available product "NOCOLOK" (manufactured by Alcan, Canada) is particularly suitable. Further, the aluminum fluoride-based flux is conveniently a fine powder. The finely divided aluminum fluoride-based flux has a thickening effect and prevents separation and sedimentation of metal powder.

When copper, silicon, magnesium is contained as a component of the material to be brazed or the melting point of the flux is lowered, it is effective to contain Cs, Sr, Ba, Zn, Cu, and fluoride, oxide or the like alone. , Mixing, and reaction products can be exemplified, and there is no limitation on the addition technique thereof, and they are included in the technical scope of the present invention.

The amount of the above-mentioned flux compounded is 0.5 to 15
Parts by weight, preferably 1 to 10 parts by weight, especially 3 to 10 parts by weight, and when it is less than 0.5 parts by weight, sufficient flux action can be obtained even by brazing in a furnace in an inert atmosphere. It is difficult to use more than 15 parts by weight, and not only it is wasteful, but also the appearance of the product becomes poor due to a large amount of white residue and black spots on the surface of the fillet, and the brazing furnace is not contaminated or corroded. Will cause problems.

The organic polymer used as the binder in the present invention is a substance containing polyalkylene oxide having an average molecular weight of 100,000 to 5,000,000, preferably 100,000 to 1,500,000 as a main constituent component in the molecule.

The viscosity of the vehicle is preferably 30,000.
This is not more than cps (20 ° C.), which not only improves the productivity of the brazing paste, but also significantly improves the usability of the brazing paste, particularly the coating property. If the molecular weight is less than 100,000, sufficient viscosity will not be obtained unless a large amount of the polymer is used for compounding, and the viscosity of the paste will increase due to the hydroxyl groups. On the other hand, if the molecular weight is too large, the spinnability becomes too strong, and the viscoelastic properties deteriorate.

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

Examples of the organic compound having two or more active hydrogens include polyhydric alcohols such as ethylene glycol, polypropylene glycol and 1,3-butylene glycol, and polyhydric phenols such as water-vaporized bisphenol and bisphenol dihydroxypropyl ether. . Examples of polycarboxylic acids include maleic acid, fumaric acid, succinic acid, glutaconic acid, adipic acid, sebacic acid, isophthalic acid, terephthalic acid and trimellitic acid.

Aromatic carboxylic acids tend to generate residual carbon on the surface of the brazing material during the brazing process. The residual carbon tends to increase in the order of succinic acid, adipic acid, and phthalic acid.

As the method for producing the high molecular weight polyalkylene oxide-containing organic polymer used in the present invention, not only general addition polymerization of alkylene oxide but also polymerization reaction using Ziegler-Natta catalyst in a suitable solvent can be used.

The polyalkylene oxyside produced in the polymerization reaction using the Ziegler-Natta catalyst is Ti,
A substance containing a small amount of metal impurities such as Al, Zn and Si is preferable, and 0.5% or less, preferably 1000 ppm or less. This type of polymer is an odorless and nontoxic substance, is stable against oxygen, ozone, acid, alkali and ultraviolet rays, and has a viscosity of 200 to 30 at room temperature when dissolved in a solvent.
Since a liquid of about 000 cps can be arbitrarily obtained, coating workability becomes easy. In the air, about 200-350
Since it decomposes completely and volatilizes at a temperature of about 300 to 400 ° C. in a nitrogen atmosphere, no carbonization residue is generated after brazing.

The amount of the organic polymer compounded in the paste is 0.5 to 15 parts by weight, more preferably 1 to 10 parts by weight, based on 100 parts by weight of the aluminum alloy powder. If it is less than 0.5 parts by weight, the effect as a binder is small,
If it is over the weight part, it is hard and the workability is poor. Further, when the amount of the polymer increases, the amount of the polymer that volatilizes increases, so that the pollution of the furnace becomes worse.

In order to adjust the coating workability and the like of the aluminum brazing paste according to the present invention, an organic viscosity modifier and a solvent are mixed just before use. You may mix | blend suitably with this paste within the limit which does not impair. The viscosity of the brazing material of the present invention is adjusted according to the coating method. For example, when it is applied by spraying, it is suitable to use a low-viscosity suspension solution in the form of shubbs, and in the case of brush application, it is suitable to use a suspension solution in the form of a sauce with a slightly higher viscosity. Or, if the anti-settling agent is not added, the aluminum alloy brazing powder will be precipitated and uniform coating cannot be performed. As described above, there are various methods of applying the suspension solution, and the optimum viscosity varies depending on the application equipment. Therefore, each solvent described in the text can be used as the solvent for forming the suspension solution. Viscosity modifiers may be used to control the viscosity of the paste.

Examples of the viscosity modifier 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. ,
Hydrogenated castor oil is preferred. The viscosity of the aluminum brazing paste according to the present invention may be appropriately selected according to the application method of the paste and is not particularly limited, but usually 5
000-500000cps / 23 ° C, preferably 150
It is 00-300000 cps / 23 degreeC.

The viscosity in this case is a value measured using a Brookfield viscometer. The choice of solvent used in the present invention is of paramount importance to the technology of the present invention.

The polyalkylene oxide resin having a molecular weight of 100,000 to 5,000,000 is a substance having a unique solubility and is not freely soluble in many solvents.

The solvent used in the present invention is preferably a solvent which dissolves the polyalkylene oxide and is safe and easy to handle by itself, and does not generate harmful gas when heated in the furnace and has a good feeling in use. . Since the polyalkylene oxide polymer having a molecular weight of 100,000 or more has lower hygroscopicity than low molecular weight glycol, performance deterioration of the aluminum paste is less likely to occur. The solvent must also be non-reactive with aluminum.

Since the conditions of use of the paste are different, there are various cases in which it is desired to evaporate quickly, and it is preferable that the evaporation is slower. Therefore, a solvent suitable for it is selected.

In the present invention, the alkylene glycols are mono- or polyalkylene glycols of alkylene oxides having an alkylene group having 3 to 4 carbon atoms or their lower alcohols from the viewpoint of solubility of organic polymers and safety of paste. A monoether having 1 to 4 carbon atoms is preferable.

Particularly preferred solvents are glycols or glycol ethers having a propylene residue and having 1 to 10 carbon atoms, specifically dipropylene glycol, tripropylene glycol, propylene glycol monomethyl ether, propylene glycol monoethyl ether and propylene glycol mono. Propyl ether, propylene glycol monoisopropyl ether, propylene glycol monobutyl ether, propylene glycol monoisobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monoisopropyl ether, dipropylene glycol Monobutyl ether, propylene glycol monoisobutyl Solvent selected from the group consisting of ether, 1,4-dioxane, the solvent selected from dibutylene glycol can be exemplified. Polyethylene glycols and their ethers are inferior to propylene-based pastes in terms of paste viscosity stability, toxicity, and safety and health.

These solvents dissolve polyalkylene oxides well, have low hygroscopicity, low reactivity with aluminum powder and high stability over time. Further, 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. Further, during brazing in the furnace, polyalkylene oxides are well evaporated so that no residual carbon is produced in the brazing part.

The reason why dipropylene glycol has a good property even though it is a solvent having two hydroxyl groups cannot be explained by mere water absorption. It is considered that this effect is due to the action due to the structure of the secondary terminal, steric hindrance, and the absence of alkoxide formation due to the reaction between aluminum and alcohol.

In the present invention, the solvent is used in an amount of 30 to 150 parts by weight, preferably 40 to 100 parts by weight, based on 100 parts by weight of the aluminum metal powder. The amount depends on the type of solvent, the type and amount of organic polymer used, the particle size and shape of aluminum metal powder, the amount used, the amount of flux, etc., but normally the viscosity of the paste is 5,000 to 500,000 cp.
s (23 ° C), more preferably 15,000 to 300,000 cps
To be

The aluminum wax paste according to the present invention may further contain conventional additives in addition to the above-mentioned components, if desired.

Such additives include antioxidants.
(Eg BHT etc.), corrosion inhibitors (eg benzotriazole), colorants (eg fluorescein, methyl orange etc.), defoamers (eg silicone oil etc.) and matting agents. Hereinafter, the present invention will be described with reference to examples. As a method of using this paste, it is advantageous for joining extruded materials where brazing sheets cannot be used and for joining ceiling portions where brazing sheets for molding brazing cannot be used. In addition, although the application of flux is essential in the current brazing method, the workability is good because the brazing material and the flux are premixed in the paste. If a dispenser or the like is used, the process can be easily robotized. The brazing material according to the shape of use is not required to be formed, and it is only necessary to apply it to the brazing material portion. Tokuhei 4-
In polybutene such as 75119, the binder component adheres to the furnace 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.

Examples 1 to 13 Aluminum braze pastes 1 to 14 according to the present invention were prepared according to the formulation shown in Table 1 below.

[0042]

[Table 1]

The footnotes in Table 1 are as follows. (1) Al-10% Si alloy powder (average particle size; 40 μm, oxygen content: 0.05%) (2) Al-10% Si alloy powder (average particle size; 70 μm, oxygen content: 0.02 %) (3) "NOCOLOK" (aluminum fluoride-based flux) (4) Polyethylene oxide having a molecular weight of 100,000 (content of metal impurities: 100 ppm) (5) Wax obtained by hydrogenating castor oil (6) Daiichi Kogyo Seiyaku Polyethylene oxide ester with a molecular weight of 100,000 (7) Polyethylene oxide with a molecular weight of 100,000 (8) Polyethylene oxide with a molecular weight of 400,000 (9) Polyethylene oxide with a molecular weight of 360-4 million (Meisei Chemical) 10) Sumitomo Seika made 20% PO with a molecular weight of 100,000, EO8
Table 1 shows the properties of the aluminum braze pastes 1 to 13 prepared by the above formulation.

Comparative Examples 1'-9 ' Aluminum braze pastes 1'-9' were prepared according to the formulation shown in Table 2 below.

[0045]

[Table 2]

The footnotes in Table 2 are as follows. (1) Al-10% Si alloy powder (average particle size; 70 μm, oxygen content: 0.02%) (2) "Nocoloc" (aluminum fluoride based flux) (3) 21% LiCl, 40% KCl, 22.5% NaCl,
9% LiF, 8.5% ZnCl ₂ (4) Polyethylene glycol average molecular weight 1000 (5) Liquid polyisoprene average molecular weight 100,000 (6) Liquid polyisobutylene average molecular weight 500

The properties of the aluminum brazing pastes shown in Tables 1 to 3 are the same as those of the sample pastes A, except that aluminum test plates 1 (2 mm × 25 mm × 60 mm) and 2 (2 mm × 15 mm) were used.
X 50 mm) and 2 in the center of one side of the T-joint made as shown in Fig. 1 (top view) and Fig. 2 (front view).
After attaching 60 mg, brazing in a furnace (6
After melting at 00 ° C., holding for 5 minutes) was performed and evaluated. The specific evaluation criteria for each property are as follows.

Metal residue ( residue of undissolved brazing metal powder) A: excellent B: good C: acceptable D: not acceptable E: not evaluated (alloy powder hardens into cement and does not return to metallic wax)

Storability of paste (separation of paste after 1 month at 25 ° C.) A: No separation B: Polymer bleeds on paste upper surface C: Separation of polymer is less than 10% D: Separation of polymer is less than 20% E: 20% or more of the polymer separates

Viscosity change A: Smooth paste state, less than 10% viscosity change B: No smoothness, no crushing, 50% viscosity change
Less than% C: A small lumpy fluff occurs and the viscosity change is 100%
Less than D: crushed bean paste, viscosity change is 100% or more E: Solid

Corrosion Corrosion after brazing (96 h) A: No corrosion is observed even after humidity treatment at 40 ° C. and 90%. B: Discolored by humidity treatment at 40 ° C and 90%. C: The color changes in the indoor environment. D: Both the base metal of the brazing material corrode in the indoor environment. E: Not evaluated (alloy powder hardens into cement and does not return to metal wax)

Detergency A: Water-soluble and easy to wash B: Can be washed with water + detergent C: Can be washed with organic solvent D: Can not remove adhered substances E: Not evaluated

Scatter A: Not scatter B: Scatter less than 5% C: Scatter less than 10% D: Scatter 10% or more E: Not evaluated

Furnace contamination A: Almost unnoticeable B: Slightly dirty, but not enough to wipe off C: Can be wiped off in a short time each time D: Can be wiped off every time, but requires a considerable amount of time E: Very dirty time I can't wipe it off

[0055]

The aluminum brazing paste according to the present invention has good storability (for example, at room temperature in air for about 6 to 20 months, metal powder and flux do not separate) and coating workability, and is excellent. Exhibits brazing characteristics. When aluminum members are brazed using the brazing paste, no poor appearance, poor bonding, or corrosion over time are observed at the joints, and the members can be welded without any additional heating step. Since excellent brazing can be performed and the paste and deposits of the brazing furnace can be washed with water, the maintenance of the brazing furnace is simple and industrially excellent.

[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 the T joint.

[Explanation of symbols]

1 ... Aluminum test plate, 2 ... Aluminum test plate
3 ... Sample paste

─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-147193 (JP, A) JP-A-4-333390 (JP, A) JP-A-3-35870 (JP, A) JP-A-6- 39586 (JP, A) JP-B 57-50598 (JP, B2) JP-B 63-43200 (JP, B2) (58) Fields investigated (Int.Cl. ⁷ , DB name) B23K 35/22-35 / 363

Claims (6)

(57) [Claims] 1. An aluminum alloy powder having an average particle size of 10 to 500 μm, 100 parts by weight, and an aluminum fluoride based flux of 0.5 to
An aluminum brazing paste for brazing an aluminum member, containing 15 parts by weight, 0.5 to 10 parts by weight of an organic polymer having polyalkylene oxide as a main constituent and having an average molecular weight of 100,000 to 5 million, and 30 to 150 parts by weight of an organic solvent. 2. The paste according to claim 1, wherein the polyalkylene oxide is a polymer of ethylene oxide and / or propylene oxide. 3. The paste according to claim 1, wherein the organic polymer is an ester and / or urethane of a polyalkylene oxide and a polyalkylene oxide mixture. 4. Alloy powder for aluminum brazing paste
The pace according to claim 1, wherein the oxygen content is 0.2% or less.
To. 5. The organic solvent is charcoal having a propylene residue.
Glycols or glycol ethers having a prime number of 1 to 10,
Select from 1,4-dioxane and dibutylene glycol
The paste according to claim 1, which is used. 6. An aluminum wax pace according to claim 1.
Applied around the joints between the aluminum members and
Aluminum parts brazed in a furnace in an inert atmosphere
How to join.