JPH06179094A - Aluminum brazing filler metal - Google Patents

Abstract

PURPOSE:To prevent appearance defects and joining defects after brazing by further incorporating a metallic powder having a sacrifice anode effect for the aluminum of a member to be joined into a brazing filler metal. CONSTITUTION:At least aluminum alloy brazer powder and flux powder are incorporated into an aluminum brazing filler metal for joining aluminum members. In the brazing filler metal, a metallic powder having a sacrifice anode affect against aluminum which is a member to be joined and aluminum alloy is further incorporated. Zinc is used for the metallic powder. Also, the metallic powder is to be 0.5-25 pts.wt. per 100 pts.wt. of aluminum alloy brazer powder. The oxygen content of aluminum alloy brazer powder is made to be 0.2wt.% or less. Consequently, ideal corrosion inhibition for the members to be joined is realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum brazing material used for joining aluminum and aluminum alloy members and for providing a sacrificial anode effect, and a joining method thereof.

[0002]

2. Description of the Related Art In recent years, in order to reduce the weight of structural bodies such as radiators, material reduction and size reduction have been attempted.
The use of aluminum and aluminum alloys is becoming popular as a material saving material, but there are two major problems. One is the problem of pitting corrosion and the other is the problem of brazing. Aluminum and its alloys form a non-corrosive oxide coating on the surface, which suppresses corrosion.However, if a part of the oxide coating is destroyed, corrosion from that portion to the inside progresses. A phenomenon called pitting corrosion occurs.
If this pitting corrosion occurs in pipes and tubes that carry liquids and gases, the life of the structure is significantly shortened. The second problem is that an aluminum alloy is used as a brazing material for brazing aluminum or aluminum alloy, but there is no suitable brazing material. Generally, an Al-Si alloy is used, but the Al-Si alloy is Al or Al-Mn which is often used as an aluminum structural material.
Since there is not much difference in melting point from the system alloys and it is necessary to strictly control the heat during brazing, it is difficult to perform extreme brazing by hand or the like.

In order to solve the first problem, an alloy of aluminum and a base metal such as zinc is used as a brazing material.
It has been proposed to use (typically Al-Si-Zn) as the sacrificial anode by using this base metal as the sacrificial anode and to preferentially corrode it to prevent pitting corrosion of the aluminum base material. A typical example thereof is a method of using a brazing sheet in which one or both sides of an aluminum base material sheet or plate is covered (clad) with a brazing material sheet containing zinc or the like. This brazing sheet is rolled into a tubular shape and its both side edges are heated and brazed (electric resistance welded tube) does not cause pitting corrosion because a base metal such as zinc on the surface acts as a sacrificial anode. However, the thickness of the electric resistance welded pipe is limited, and it cannot be used for thinner tubes. Further, the complicated structure due to the miniaturization of the structure causes a case where the electric resistance welded pipe or the brazing sheet cannot be used, and in that case, the brazing of the details is performed with a lot of trouble.

This method has a second problem that not only the working efficiency but also the fine adjustment of the brazing temperature cannot be performed. The second problem is to apply or braze a brazing material in place on the structure to be brazed, and then
This can be solved by melting and casting or diffusing only the brazing filler metal by placing the brazing filler metal in a furnace which is maintained at a temperature that melts only the brazing filler metal without melting the base metal.

Paste-like brazing materials used for such purposes are disclosed in JP-A-54-43853 and JP-A-2-1471.
No. 93, JP-A-2-268995 and the like. However, the brazing material disclosed in the above publication is Al-Si-
This is a Zn-based alloy powder made into a paste. When this paste is placed and applied to a braze, zinc does not diffuse like silicon, and as a result, zinc does not move to the flowed brazing material tip. Therefore, there is a problem that pitting corrosion is caused because the brazing filler metal tip that has flowed does not function as a sacrificial anode.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above problems, and a brazing filler metal composition for effectively achieving the brazing of details of a complex aluminum structure and the prevention of pitting corrosion, and the use thereof. It is an object of the present invention to provide a method for joining aluminum members.

[0007]

The present invention relates to an aluminum brazing material for joining aluminum members, which contains at least an aluminum alloy brazing powder and a flux powder, wherein the brazing material is aluminum and an aluminum alloy to be joined. The present invention also relates to an aluminum brazing material, which further contains a metal powder having a sacrificial anode effect.

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 a trace amount of bismuth, tin as a third additive element, (A metal containing barium is shown), and aluminum-copper alloy powder can be used, and aluminum alloy braze may contain zinc, tin, barium, or the like.

The aluminum alloy brazing powder preferably has an average particle size of 10 to 500 μm, more preferably 40 to 150 μm. If it is less than 10 μm, the specific surface area of the powder becomes excessively large, and the amount of oxide film substances increases, so that it becomes difficult for the powder particles to be fused and integrated sufficiently. If it exceeds 500 μm, the powder is kneaded with the binder. In this case, not only it becomes difficult to disperse and suspend, but also the interval between the powders becomes too large, which makes it difficult to perform precise brazing.

The oxygen content of the aluminum alloy powder is 0.
It is 2% by weight or less, preferably 0.1% by weight or less. If it is more than 0.2% by weight, the oxide film becomes thicker,
Since aluminum is particularly strong, it is necessary to add 20 parts by weight or more of the flux necessary to destroy the oxide film. However, if 20 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, and it also adversely affects the brazing furnace. The shape of the aluminum alloy powder is not particularly limited, and examples thereof include a spherical shape, an irregular shape, a needle shape, and a flake shape. As such an aluminum alloy powder, one produced by an atomizing method is industrially advantageous.

As the flux that can be used in the present invention,
Aluminum fluoride type flux such as AlF ₃ -KF, KAlF ₄ -K ₃ AlF ₆ and KAlF ₄ and chloride type flux can be exemplified, but aluminum fluoride type flux, especially commercially available product “NOCOLOK 100” is preferable. . The amount of the above-mentioned flux compounded is 0.5 to 15 parts by weight, preferably 0.5.
If it is less than 0.5 parts by weight, it is difficult to obtain a sufficient flux action, and if it is more than 15 parts by weight, the effect of the flux action is the same. Do not bring.

In the present invention, the most characteristic requirement is that, in addition to the aluminum alloy brazing powder, a metal baser than aluminum, especially zinc powder, is incorporated into the brazing material. Therefore, not only the brazing material powder but also the powder containing the sacrificial anode component as an alloy is not controlled. For example, as described above, in the conventional brazing material of Al-Si-Zn alloy, Zn in the molten brazing material becomes less diluted toward the tip and does not diffuse, so that the tip acts as a sacrificial anode. It causes pitting corrosion, but the base metal is carried to the tip of the molten brazing filler metal only by mixing it into a single powder without alloying it with a metal powder that is less base than aluminum. And prevents pitting corrosion.

Zinc as a metal having a sacrificial anode effect,
Examples include tin, indium, barium, silver, cadmium, gallium, and zinc is particularly preferable.

The amount of the metal powder having the sacrificial anode effect added is 0.5 to 25 parts by weight, preferably 1.5 to 15 parts by weight, based on 100 parts by weight of the aluminum alloy powder. When the amount is small, the effect of addition, that is, the sacrificial anode does not work. If it is more than 25 parts by weight, the effect of addition is sufficient. If it is added more than 25 parts by weight, the corrosion becomes severe and the adverse effect is produced. In addition, the metal having the sacrificial anode effect does not sufficiently diffuse and flow, so Liquidity is impaired.

With respect to the metal powder having the sacrificial anode effect to be mixed, there is no problem as long as the average particle size is 500 μm or less, preferably 150 μm or less, and the shape is preferably spherical so that it easily flows. This is because even if the mixed metal powder having the sacrificial anode effect is fine and the amount of the oxide film is large, the oxide film is not as strong as aluminum, so the oxide film is easily broken and fusion fusion can be easily performed. Also, the smaller the average particle size, the larger the contact area with the aluminum alloy powder, so that it is easy to alloy and is preferable.

As described above, zinc powder is preferred as the metal powder having the sacrificial anode effect. This is because zinc has a large sacrificial anode effect and a large amount of solid solution with aluminum, so that it easily diffuses and alloys with the aluminum alloy brazing powder during brazing. Moreover, since the vapor pressure is high and the melting point is lower than that of the aluminum alloy brazing powder as described above, zinc is distributed more toward the surface of the brazing material and less toward the base material. Therefore, the surface of the potential distribution is base and becomes more noble the closer it gets inside, the closer it is to the surface, the greater the sacrificial anode effect becomes, and corrosion tends to occur in the surface layer and does not corrode deeply in the vertical direction. It is hard to eat. Therefore, it is extremely effective in suppressing pitting corrosion.

As to the particle size, as described above, particularly for zinc powder, it is more effective to be fine and spherical, and even if the amount of oxide film is large due to its fineness, the vapor pressure is high, so the oxide film can be easily destroyed. This is because, since they melt and flow and diffuse with the aluminum alloy brazing powder, they do not remain as metal residues, and when they are spherical, they easily flow.

Zinc powder is produced by a distillation method or a spraying method, but it can be used by anyone, and when it is obtained, it is widely used for dry batteries, rust-preventive paints, etc., so it can be easily obtained and still, Low price and no quantitative restrictions.

Regarding the oxygen content of the metal powder having the sacrificial anode effect, if the addition amount is too large as described above, it will cause a problem, but if it is within the addition amount range of the present invention, it will hardly cause any problem, so that it is not particularly limited. .

Further, the amount of addition can be freely adjusted by separately mixing the metal powder having the sacrificial anode effect, and it is not necessary to prepare various kinds of powders having different amounts of addition like the alloy powder. Cost effective,
There are few inventories and varieties, and there are industrial advantages.

By using the brazing material of the present invention, a conventional brazing material (brazing sheet, brazing paste) produces a sacrificial anode effect even when it is difficult to braze it. Is also useful.

The brazing material of the present invention can be dispersed and coated with various viscosities and binders depending on the coating method. For example, when applying by spraying, it is suitable to use a low viscosity viscous suspension solution, and for brush application, a slightly viscous source suspension solution, which must be stirred. If an anti-settling agent is not added, the aluminum alloy brazing powder will precipitate and uniform coating cannot be performed. As mentioned above, there are various coating methods using a suspension solution, and the optimum viscosity also differs depending on the coating equipment. A non-polar solvent and a medium molecular polymer can be used as a dispersion medium for forming a suspension solution, and examples thereof include hexane, toluene, xylene, an isoparaffin solvent, liquid polyisobutylene having an average molecular weight of 300 or less, and / or its hydrogenated product. I can. Water can also be used as the dispersion medium for a short period of time during on-site construction.

A paste is suitable for overlaying the joint. In the case of a paste, if the viscosity is not high enough to build up the paste, the dispersion medium and the brazing filler metal powder are separated into two layers, and the build-up cannot be done, so it cannot be used. Therefore, it must be a paste-like brazing material that is uniformly dispersed. Therefore, liquid polyisobutylene having an average molecular weight of 300 to 2000 and / or a hydrogenated product thereof is preferable as a binder that is uniformly dispersed and does not generate a carbonization residue. Since such a medium molecular polymer is odorless, nontoxic, and inert, it is convenient for this type of pasting. When the average molecular weight of the liquid polyisobutylene and / or its hydrogenated product is less than 300, the dispersion medium and the brazing filler metal powder cannot be built up by separating into two layers as described above without the anti-sedimentation agent. or,
When the average molecular weight is more than 2000, the viscosity becomes very high, so that the coating workability is deteriorated and the brazing property is also poor.

The binder content is preferably 30 to 80 parts by weight, and when it is less than 30 parts by weight, it becomes messy and does not form a paste. On the other hand, if the amount is more than 80 parts by weight, the two layers are separated, the paste is not formed, and the metal content is low.

With respect to the above-mentioned aluminum brazing filler metal, an organic viscosity modifier or an anti-settling agent is used to adjust the coating workability by a coating device such as a dispenser within a range that does not impair the action and effect of the compounding ingredients. , May be blended appropriately. Examples of the viscosity modifier include synthetic wax, petroleum wax, hardened oil, hardened castor oil, fatty acid amide, polyamide and the like. The solvent is as described above.
Hereinafter, the present invention will be described with reference to examples.

[0026]

Example An aluminum brazing material was prepared according to the formulation shown in Table 1. Attach each aluminum brazing material (3) at right angles to the surface of the aluminum test plate (1) (2 mm x 25 mm x 60 mm) of material A3003 (2) (2 mm x 15 mm x 50 mm)
As shown in Fig. 1 (top view) and Fig. 2 (front view), 260 mg was applied to the central part on one side of the T joint obtained by temporary fixing, and then brazing in a furnace in an argon stream (melting at 600 ° C) Then, each test piece was evaluated by using the test piece.

[0027]

[Table 1]

The footnotes in Table 1 are as follows. (1) Aluminum alloy powder Al-10Si (average particle size 70 μ, oxygen content 0.03
%) Al-10Si (average particle size 40 μ, oxygen content 0.05
%) Al-10Si-3Zn (average particle size 70μ, oxygen content 0.03%)

(2) Zinc powder, average particle size 8μ, oxygen content 0.50%, average particle size 50μ, oxygen content 0.15% (3) Flux "NOCOLOK Flux 100" manufactured by Alcan Co., Ltd. (4) Binder component Liquid polyisobutylene (average molecular weight 500, viscosity 20
5cSt / 40 ℃) "High Wax 110P" manufactured by Mitsui Petrochemical Co., Ltd.

For corrosion evaluation, a corrugated test plate (2) (0.1 mm × 25 mm × 50 mm) of the same material was placed on an aluminum test plate (0.5 mm × 25 mm × 60 mm) of material A1050 as shown in Fig. 3 (plan view). ), FIG. 4 (front view) and FIG. 5 (left side view), and temporarily fix the aluminum test plate 1 to the right end in the longitudinal direction with a width of 5 mm, and to fill the width of the test plate with the aluminum brazing material (3) 1.
After applying 50 mg, it was brazed under the above-mentioned conditions. CA
The SS test was performed for one month, the vicinity of the tip of the brazing material of each test piece was cut, and observed with an optical microscope. The evaluation was carried out on a test plate.

Table 2 shows the evaluation results. The specific criteria for each evaluation are described after Table 2.

[Table 2]

Evaluation Criteria Metal Residue A: Excellent B: Good C: Possible D: Not possible E: Not applicable (Brazed material does not melt)

Appearance due to flux residue A: Excellent B: Good C: Possible D: Not possible E: Not evaluated

Wax fluidity A: Fillet formation rate of 100% B: Fillet formation rate of 80% to less than 100% C: Fillet formation rate of 50% to less than 80% D: Fillet formation rate of less than 50% E: Non-evaluated fillet formation The rate is defined as a percentage of the length (mm) of the fillet with respect to the length (50 mm) of the vertical wall of the T-joint described above.

Fillet shape (fillet thickness) A: Most of the brazing material gathers in the fillet and draws an arc with optimum tension. B: About 70% of A fillets are formed. About 30% of C: A fillets are formed. D: Fillet is not formed. E: Not applicable for evaluation (the brazing material does not melt)

Corrosion (Potential Corrosion of Cross Section) A: Maximum pitting depth of less than 0.1 mm B: Maximum pitting depth of 0.1 mm or more and less than 0.25 mm C: Maximum pitting depth of 0.25 mm or more Less than 5 mm D: Penetration E: Not evaluated

[0037]

EFFECTS OF THE INVENTION The aluminum brazing material according to the present invention does not cause brazing characteristics, that is, poor appearance after brazing and poor joining. Further, it was not possible with the existing brazing material to diffuse the brazing material to have a sacrificial anode effect, but in the brazing material of the present invention, there is a metal having a sacrificial anode effect even at the tip of the brazing material, In addition, since the concentration becomes higher toward the surface, it is possible to ideally prevent corrosion of the members to be joined. According to the brazing material of the present invention, it is possible to perform brazing even in a shape in which a conventional brazing sheet cannot be used, and since the sacrificial anode effect is provided up to the leading end of the brazing material, brazing of the heat exchanger is possible. . Especially for automobiles, it is possible to design without being restricted by brazing sheets, etc.
Useful for lightweight and compact.

[Brief description of drawings]

FIG. 1 is a plan view of a T-joint used in Example 1.

FIG. 2 is a front view of the T joint used in Example 1.

[Fig. 3] Plan view of a test piece for corrosion evaluation

[Fig. 4] Front view of test piece for corrosion evaluation

[Figure 5] Left side view

[Explanation of symbols] 1. Aluminum test plate 2. Aluminum test plate 3. Aluminum brazing material

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tadashi Takemoto 5-11-28-506 Kasuga-cho, Toyonaka-shi, Osaka (72) Inventor Tatsuyuki Ujie 3-6-8, Kutaro-cho, Chuo-ku, Osaka-shi, Osaka Toyo Aluminum Co., Ltd.

Claims (5)

[Claims] 1. An aluminum brazing material for joining aluminum members, which contains at least an aluminum alloy brazing powder and a flux powder, wherein the brazing material has a sacrificial anode effect on aluminum and an aluminum alloy, which are the members to be joined. An aluminum brazing material further containing the powder of 1. 2. The aluminum brazing material according to claim 1, wherein the metal powder having a sacrificial anode effect is zinc. 3. A metal powder having a sacrificial anode effect is 0.5 to 25 per 100 parts by weight of an aluminum alloy brazing powder.
The aluminum brazing material according to claim 1 or 2, which is parts by weight. 4. The aluminum brazing material according to claim 1, 2 or 3, wherein the oxygen content of the aluminum alloy brazing powder is 0.2% by weight or less. 5. An aluminum brazing material containing at least 0.5 to 25 parts by weight of zinc powder and 0.5 to 15 parts by weight of flux powder per 100 parts by weight of aluminum alloy brazing powder, around the joint between aluminum members. A method for joining aluminum members, comprising the step of applying to aluminum.