JP2721912B2 - Powder brazing filler metal for aluminum - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a powdered brazing material for aluminum.

In this specification, “%” means “weight”.

Conventional technology and its problems Conventionally used brazing filler metals for aluminum include Al-Si alloys containing Si near the eutectic concentration, or In general, Cu is added.

Brazing methods are roughly classified into a method requiring flux (flux method) and a method not requiring it (fluxless method). The flux is used to break the oxide film on the surface of the base material and improve the wettability between the base material and the brazing material. Most of such fluxes have a chlorine-based composition and are highly corrosive to aluminum, so they need to be washed and removed immediately after brazing. However, in the flux method, not only the flux itself is expensive, but also it is necessary to take thorough measures against pollution, such as equipment for cleaning flux, associated drainage equipment, and treatment of harmful fume generated during brazing. Yes, economically problematic.

In order to eliminate such disadvantages of the flux method, fluxless methods such as a vacuum brazing method and an inert gas brazing method have been widely used in recent years. This fluxless method is applied to the brazing of special fields such as aircraft and space planes from the beginning to the radiators, intercoolers and oil coolers for automobiles, etc .; evaporators and condensers for air conditioners. It has become. Conventionally, brazing sheet is mainly used for brazing by such a fluxless method. However, brazing is used for brazing of a complicated shape portion, a joint portion between different diameter pipes, a U vent of a heat exchanger, and the like. It is believed that powdered brazing materials are more advantageous. Because, when using a powdered brazing material, it is only necessary to apply the brazing material only to places where brazing is required, so that not only the amount used is reduced, but also an appropriate solvent, wax, etc. This is because, by mixing with (a) and (b), direct application to a portion to be joined becomes possible, and an advantage that workability is improved is also obtained.

However, in spite of the above advantages, the powdery fluxless method has not always been widely adopted. This is because powdery fluxless brazing filler metals for fluxless processing have not yet been obtained with satisfactory performance. In other words, in the existing powdered brazing material, since a strong oxide film exists on the powder surface, the outflow of the molten metal inside the powder during the brazing operation is prevented, and many voids are formed in the brazing portion. This is because a sufficient bonding strength cannot be obtained.

Means for Solving the Problems The present inventor has conducted intensive studies in view of the above problems of the powdery brazing material used in the fluxless method, and as a result, has found that Al-Si alloy powder and Mg-Al System alloy powder or pure
It has been found that a brazing material exhibiting good brazing properties can be obtained when blending the Mg powder at a specific ratio.

That is, the present invention provides the following brazing powder for aluminum: (a) an Al-Si alloy powder composed of 8 to 20% of Si and the balance of Al, and (b) 10 to 99.99% of Mg and a balance of Al Mg-A consisting of
It consists of a mixture of l-based alloy powder or pure Mg powder, Si5 ~ 15
%, Mg 0.6 to 8% and the balance Al.

(A) An alloy powder consisting of 8 to 20% of Si, 0.01 to 2% of Mg and the balance of Al and (b) a mixture of an alloy powder of 10 to 99.99% of Mg, 0.01 to 8% of Si and the balance of Al; Fifteen
%, Mg 0.6 to 8% and the balance Al.

In the present invention, a mixture of an Al-Si alloy powder having a specific Si content and a Mg-Al alloy powder or a pure Mg powder having a specific Mg content is used, and the Si content and the Mg content in the mixture are used.
Content is within a specific range.

First, (a) Al-Si alloy powder contains 8 to 20% of Si. In this alloy (a), if the Si content is less than 8% or the Si content exceeds 20%, the melting point of the alloy becomes too high, which is not preferable. Al-Si
The particle size of the system alloy powder is preferably about 10 to 100 μm in average particle diameter. If the particle size of the Al-Si alloy powder is coarse, the gap between the powders becomes too large, so that a dense brazed portion cannot be obtained. On the other hand, when the particle size of the powder is too small, the specific surface area of the powder becomes large, so that the amount of the oxide film increases, which hinders melting during brazing. Such an Al-Si alloy powder is manufactured by, for example, an atomizing method.

(B) The Mg-Al-based alloy powder contains 10 to 99.99% of Mg. If the amount of Mg in this alloy (b) is less than 10%, the amount of Mg evaporated during brazing will be insufficient.
Destruction of the oxide film on the powder surface is unlikely to occur. The particle size of the Mg-Al-based alloy powder and the pure Mg powder is 10 to 100 in average particle diameter.
It is preferable that the thickness be about μm. When the particle diameter of the Mg-Al alloy powder or the pure Mg powder is coarse, the gap between the powders becomes too large, so that it is difficult to obtain a dense brazed portion. On the other hand, if the particle size of the powder is too small, the specific surface area of the powder becomes large, as described above,
The amount of the oxide film increases, and the flow of the molten metal during brazing is hindered. Such Mg-Al-based alloy powder and pure Mg powder are produced by, for example, an atomizing method, a pulverizing method, or the like.

(A) The mixing ratio of the Al-Si alloy powder and the (B) Mg-Al alloy powder and / or pure Mg powder is such that the Si content in the mixture is 5 to 15% and the Mg content is 0.6 to 8%. What should be done is. The Si content in the mixture is less than 5% or
If it exceeds 15%, the melting point becomes high, so that it is necessary to perform the brazing operation at a high temperature, and there is a possibility that the base material may be melted. Mg evaporates during use and causes destruction of the oxide film of the base material and brazing material itself,
If this amount is less than 0.6%, the oxide film will not be sufficiently broken, and the brazing property will not be improved. When the Mg content exceeds 8%, the brazing surname is good, but the contamination in the brazing furnace becomes severe, and erosion of the base material is liable to occur.

In the Al-Si alloy used in the present invention, Mg is substituted for part of Al and / or Si in a range not exceeding 2% of the alloy weight, more preferably in a range of 0.01 to 2%. You may make it contain. 8% of the alloy weight for Mg-Al alloys
Within the range not exceeding, more preferably within the range of 0.01 to 8%.
Si may be contained instead of part of Al and / or Mg. However, in each case, the Al-Si alloy powder and
The amounts of Si and Mg in the mixture with the Mg-Al-based alloy powder and / or the pure Mg powder should be within the above-mentioned quantitative ranges.

Further, the Al-Si-based alloy and / or the Mg-Al-based alloy used in the present invention may contain other metals as necessary. For example, Cu, Zn, and the like, which have been conventionally used to lower the melting point of the brazing material, can be used for the same purpose. The upper limit of the blending amount of Cu and / or Zn is 8% of the weight of the powder mixture. Furthermore, Bi, Be, and S have high vapor pressure and are effective in destroying oxide films.
At least one of r, In, and Pb can be used. Their usage is less than 0.2% for Bi, Be, S
In the case of r, In, Pb, etc., the total amount is 0.05% or less.

The brazing filler metal according to the present invention is prepared by mixing an Al-Si alloy powder, an Al-Mg alloy powder (and / or a pure Mg powder) and a binder component such as wax and resin with isopropanol, toluene, carbon tetrachloride in a conventional manner. After kneading uniformly in the presence of an organic solvent such as, for example, the organic solvent is evaporated.

Action and Effect of the Invention When brazing is performed using the brazing material according to the present invention, when heating, first, Mg in Mg-Al-based alloy powder or pure Mg powder
However, due to the high vapor pressure, the powder passes through the oxide film on the powder surface and evaporates, so that the oxide film becomes porous and easily broken. The evaporated Mg further combines with the oxygen remaining in the atmosphere, lowering the oxygen partial pressure in the system to prevent the oxidation of the powder and the base material, and the aluminum oxide film present on the brazing powder and the base material surface. (This is commonly referred to as the O ₂ getter effect). Mg like this
By the two actions of the Mg-Al based alloy powder (and / or
The oxide film of the pure Mg powder) and the Al—Si alloy powder is easily broken, and the molten metal flows. Furthermore, the concentration gradient due to the difference in composition between the Mg-Al-based alloy powder and the Al-Si-based alloy powder becomes the driving force, and the diffusion of alloy components at the interface between the two powders becomes active. Divided or destroyed.

As a result, the flowability of the brazing material is increased, and the wettability of the base material is also improved, so that good brazing properties are achieved.

The brazing material of the present invention can be used not only for vacuum brazing but also for inert gas brazing.

Examples Examples and comparative examples are shown below to further clarify the features of the present invention.

Example 1 An alloy having a composition shown in Table 1 below (Al-Si system: Al other than Si and Mg is Al) and Table 2 (Mg-Al system: Al other than Mg and Si) is used. Thus, an alloy powder was manufactured by an air atomizing method.

Combine and mix each kind of powder selected from the above two alloy powder groups (amount passed through a 100 mesh screen) to a total of 150 g, add 3.0 g of wax and 30 g of toluene, and add a V-type blender. After kneading for 30 minutes, the toluene was evaporated to obtain a wax-containing powder brazing material.

Next, as shown in FIG. 1, a ring (3) of stainless steel (SUS304) having an inner diameter of 10 mm and a height of 3 mm was placed on an aluminum plate (1) (A3003) having a thickness of 2 mm,
2 g of the brazing material (5) obtained above was placed in the ring and heated at 600 ° C. for 5 minutes in a vacuum furnace under a reduced pressure of 1 × 10 ⁻⁵ Torr. After the heating is completed, the whole is taken out of the furnace, air-cooled, the ring is removed, the solidified brazed part is rubbed with a wire brush, and the weight of the remaining brazed part is measured. (Hereinafter referred to as contribution ratio).

Mixing ratio of the two alloy powders in Table 3 (Upper: Al-Si based: Mg
-Al system) and the contribution ratio (lower =%) are shown.

Example 2 In the same manner as in Example 1, Al-Si alloy powder and Mg-Al alloy powder (both passed 325 mesh) having the following compositions were produced.

* Al-Si alloy powder: No.6 ... 13Si-0.3Mg No.7 ... 15Si-1.5Mg * Mg-Al alloy powder: No.8 ... 10Mg-3Si No.9 ... 20Mg-5Si No.10 ... 40Mg-1Si Next, a brazing material was prepared in the same manner as in Example 1 by combining one kind selected from the above two alloy powder groups, and the brazing property was examined in the same manner as in Example 1.

 Table 4 shows the results.

As is clear from the comparison between Tables 3 and 4, it is clear that the smaller the particle size of the powder, the better the brazing properties.

Example 3 The brazing material of the present invention was prepared by combining the Al-Si alloy powder No. 3 obtained in Example 1 with the Mg-Al alloy powders Nos. 2 and 3, and the atmosphere gas in the furnace was changed to N. _The brazing properties were examined in the same manner as in Example 1 except that _two gases were used.

 Table 5 shows the results.

From the results shown in Table 5, it is clear that the brazing material of the present invention shows good brazing properties even in an N ₂ gas atmosphere.

Comparative Example 1 Using the same aluminum plate and stainless steel ring as used in Example 1,
-13Si-0.3Mg powder and O
Al-40Mg-1Si powder was arranged as _two getters, and the brazing property was evaluated in the same manner as in Example 1.

As a result, diffusion of alloy components at the interface between the two powders cannot occur only by the O ₂ getter function of the Al-40Mg-1Si powder,
It turned out that sufficient brazing properties could not be obtained.

[Brief description of the drawings]

FIG. 1 is a plan view showing an outline of a test apparatus used for measuring the brazing property in the embodiment of the present invention. (1) Aluminum plate (3) Stainless steel ring (5) Brazing material

Continuation of front page (72) Inventor Akira Tanaka 3-6-8 Kutarocho, Chuo-ku, Osaka-shi, Osaka Inside Toyo Aluminum Co., Ltd.

Claims (2)

(57) [Claims] (1) Al-S comprising 8 to 20% of Si and the balance being Al
Aluminum consisting of i-alloy powder and a mixture of Mg-Al-based alloy powder or pure Mg powder consisting of 10 to 99.99% of Mg and the balance of Al, and 5 to 15% of Si, 0.6 to 8% of Mg and the balance of Al Powder brazing material. 2. A) Si 8 to 20%, Mg 0.01 to 2%, and balance A
alloy powder consisting of l and (b) Mg10-99.99%, Si0.01
~ 8% and the balance of alloy powder consisting of Al,
A powder brazing filler metal for aluminum comprising 5 to 15% of Si, 0.6 to 8% of Mg and the balance of Al.