JPS5823197B2 - Aluminum flux - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a brazing alloy for aluminum brazing elbows that does not use flux, and specifically, in brazing in a non-oxidizing gas atmosphere or a vacuum atmosphere without using flux, Aluminum brazing aims to provide a brazing alloy that has better wettability and workability than the brazing alloy used.

Conventional brazing alloys for aluminum are generally based on the A7-8i alloy, but the brazing alloy for vacuum brazing, which has recently been industrialized, is AA-8i with a small amount of Mg.
Bi, Be, St, Sb, etc. are added to the Al-8i alloy for brazing in a non-oxidizing gas atmosphere.

When the above-mentioned conventional brazing alloys are applied to complex structures, pipes, fittings, etc., the fillet formation of the molten solder may occur in both non-oxidizing gas atmospheres and vacuum atmospheres. There was a sense of dullness.

That is, in order to obtain a satisfactory fillet, stricter joint gaps and shapes are required than in conventional brazing using flux.

For example, in the vacuum brazing of a radiator, the melted solder that joins a flat tube and a header plate has a drawback that it is difficult to flow into the joint, making it difficult to form a good fillet.

Furthermore, vacuum brazing has the disadvantage that Mg as an alloying element evaporates during brazing and contaminates the furnace, and there are attempts to reduce the amount of Mg as much as possible.

However, if Mg is reduced too much, it is difficult to form a satisfactory fillet.

By improving the wettability and spreadability of the brazing material, the present invention provides better brazing properties than conventional brazing alloys both in a non-oxidizing gas atmosphere and in a vacuum atmosphere.

As a result of studying the addition of basic elements, the present invention discovered that Al
This is based on the discovery that the addition of gallium (G(II)) to the -8i braze is effective in improving the wettability of the brazing material and reducing the surface tension of the molten alloy.

Furthermore, it has been found that when Ga, which is the basis of the present invention, is added to an Al-81-Mg alloy for conventional vacuum brazing, the vacuum brazing properties are further improved.

In other words, when Ga and Mg coexist, the Mg content can be lower than that of the brazing alloy used in conventional vacuum brazing.

This can be one means for reducing furnace contamination due to Mg evaporation, which is a problem in vacuum brazing.

The gist of the present invention is to apply an Al1-8j alloy containing Si 7.0 to 15.0 or an AA-8i-Mg alloy containing Si 7.0 to 15.0 and Mg 0.3 to 3.5. The fluxless brazing of aluminum is a brazing alloy that is characterized by adding Ga of 0.0001 to 1.0.

Next, the functions of each component will be described.

Si lowers the melting point of the brazing filler metal and increases its fluidity, but
If it is less than 7.04, no effect will be observed, and if it is more than 15, the melting point will suddenly rise, making it impossible to use it as a brazing material.

Also, when used as a skin material for praising sheets,
The diffusion of Si in the molten solder into the core material becomes significant.

When Ga is less than 0.0001%, it is ineffective in improving wettability and reducing surface tension, and when it is more than 1.0%, corrosion resistance deteriorates and costs increase.

In vacuum brazing, Mg added to the brazing alloy used evaporates in a vacuum and generates Mg vapor, which combines with oxygen in the atmosphere to remove it, and also removes moisture from the atmosphere, further producing alumina ( A1203) is reduced.

This reaction is ineffective if the amount is less than 0.3%, and if it is more than 3.5%, the workability of the brazing filler metal deteriorates and the furnace becomes noticeably contaminated by Mg vapor.

The reason why AA Si Mg Ga brazing alloy has better wettability in vacuum brazing is firstly due to M.
g acts to promote wetting of the molten solder with the base metal, and Ga in the molten solder further promotes this and lowers the surface tension,
It is thought to improve wettability.

Other unavoidable impurities in the normal range (e.g. Mn, C
r, Cu, Fe, Zn, Ti, etc.) do not affect brazing properties even if they are contained in trace amounts.

Figure 1 shows diameter 1 in vacuum atmosphere and N2 gas atmosphere.
A spread test was conducted on various brazing fillers with a thickness of 5U and 2D, and the spread area was measured and compared in a graph.

The solid line graph shows the spread area in a vacuum atmosphere, and the dotted line graph shows the spread area in a N2 gas atmosphere.

As is clear from the spread results in a vacuum atmosphere, the spread area of the Ga-containing brazing alloy is greater than that of the Al-108i-1,5Mg alloy used for normal vacuum brazing at any temperature. It is clear that the alloy of the present invention exhibits excellent wettability.

In addition, Al1-10Si-0,03Ga alloy was heated with N2
When a spreading test was conducted in a gas atmosphere, the spreading result of the same alloy in a vacuum was slightly inferior to that of the same alloy.
A better spread than the -108i-1,5Mg alloy was obtained.

In addition, the A1j-81-Ga brazing alloy is M
g There was no contamination of the furnace by steam.

The galvanic alloy of the present invention is normally applied to brazing in a non-oxidizing gas atmosphere or vacuum atmosphere, but it is also fully applicable to brazing in the atmosphere using flux. .

Example 1 Al-1,2%Mn alloy is used as the core material, and Al
-10.5% Si-0.03% Ga brazing alloy was clad with a coating ratio of 10 to form a plating sheet with a thickness of 1.2 mm.

Using this plating sheet as a partition plate, corrugated 0.16 mm thick AA3003 alloy fin materials were alternately stacked to assemble a heat exchanger model.

This model was set in a stainless steel jig and heated in a vacuum furnace to 2.5
When brazed by holding at 05°C for 3 minutes, a good fillet was created in the brazed area, and the inside of the furnace was not contaminated.

Example 2 AA-10 was used as the skin material of the plating sheet of Example 1.
, 5%S j -1,5%Mg-0,03%Ga alloy clad and corrugated 0.16mm thick AA3003 alloy fin materials using this plating sheet as a partition plate are stacked alternately in a heat exchanger. Assembled the model.

This model was set in a stainless steel jig and heated to 60°C while being evacuated to 2.5X10-5 Torr in a vacuum furnace.
When brazed by holding at 5° C. for 3 minutes, a fillet larger than the fillet created in Example 1 was formed in the brazed joint, and good brazing was obtained.

[Brief explanation of drawings]

FIG. 1 is a diagram comparing the spread areas of the alloy of the present invention and a conventional brazing alloy in a vacuum atmosphere and an N2 gas atmosphere.

Claims (1)

[Claims] I Fluxless brazing of aluminum is used, characterized by adding Ga of 0.0001 to 1.0 to an Al-8i alloy containing Si of 7.0 to 15.0. alloy. 2 0.0001-1.
Fluxless brazing of aluminum characterized by the addition of 0% Ga is a used brazing alloy.