Hello to my dear readers! aluminium Brazing process interested me 5 years ago, when I had to urgently solder the cooling radiator of my Grasshopper. Below I will show his photo and the place of soldering on the radiator, which is still working.

Recently someone asked me what is the best way to solder aluminum? I decided to read all the sane articles and personal opinions on aluminum soldering and put it on one page. This is how this article was born. Go!

What is aluminium Brazing process?

Brazing is the welding process where the addition of a metal other than the base metals is used. The particularity of the process is in the capillarity action that the material to be added exerts under the joint.

Furthermore, we fix the parts very close together. And we carry the work through a molecular junction between the surfaces of the metal, with no fusion between the base material and the addition material.

There are currently a series of addition rods containing many alloys with nickel, silver, gold, etc. The addition rod has a melting point and the application of flow is necessary to allow good capillarity of the rod during brazing.

What is the heat variation in aluminium Brazing process?

As the melting point of the addition materials is generally low. We can carry aluminium Brazing process using mixtures of combustible gases and low heat transfer atmospheric air. This equipment is common as the air-gas type and is generally used in piping and refrigeration equipment.

The brazing uses an addition rod that melts at temperatures above 450c º. Similarly, it can vary according to the alloy and the base metals of the junction can be of different nature.

Basically, brazing can use both air-fuel and oxy-fuel flames. In industrial processes of high production scales such as the production of air conditioning, refrigerators, radiators, etc ... automated brazing stations are used.

What are the common applications of brazing?

Generally, aluminium Brazing process is more common to steel joints, and the addition material used is bronze, supplied on rods that immerse in the flow or that already have the flow in a superficial layer.

In practice, the steel uses heating to a reddish color at the point where the addition material can melt, and the action of the flow creates a resistant adhesion layer.

Generally, the resistance of a brazed welded joint is less than that of an oxy-flame welded joint.

The advantages of brazing welding are:

• The application of lower temperatures implies less warping of the part;
• The steel parts to be welded do not need to be fully cast to generate the joint;
• We can weld base materials of different nature, which is not possible in flameproof welding.

Why aluminum is badly soldered?

Anyone who has tried to solder aluminum knows that ordinary solder does not stick to it at all. This is due to the stable aluminum oxide film, which has poor adhesion to the solder. Moreover, this film covers aluminum and its alloys very quickly. You will not have time to clean it - the light metal has already oxidized.

Therefore, all aluminium Brazing process and soldering methods fight first with the film, and then take care of adhesion.

How to remove oxide film?

Aluminum oxide film is removed in two ways: mechanical and chemical. In addition, both methods remove alumina in an airless environment, that is, without oxygen. Let's start with the most difficult, but the most correct and reliable method of removal - chemical.

Use oil without water

The second most difficult method is the removal of aluminum oxide under the oil film... In this case, the oil should contain a minimum of water - transformer or synthetic oil is suitable. Furthermore, you can hold the oil at a temperature of 150 - 200 degrees for several minutes so that water evaporates from it and it does not splash when heated.

Generally, under the oil film, you also need to deal with the removal of oxide. Similarly, you can rub with sandpaper, scratch with a scalpel, or use a serrated sting. Moreover, when I needed to solder the engine cooling radiator, I subtracted the chip method. We take a nail; file it with a file to get steel shavings. Next, apply oil to the place of soldering and pour in shavings.

Soldering vs brazing aluminum

With a soldering iron with a wide sting, we are trying to rub the soldering point, so that there are chips between the tip and the aluminum. In the case of a massive radiator, I additionally heated the tinning placehot air soldering station...

Then we take the solder on the tip with a drop, immerse it in the oil at the soldering point and rub it again. Moreover, for better tinning, rosin or other flux we can add. The so-called submerged arc surfacing takes place. Furthermore, the video shows a good illustration of soldering aluminum with oil.
Solder for brazing aluminum

Solders for aluminium Brazing process often made mostly of aluminum or zinc. Manufacturers add various additives to the composition to improve the properties of solders: lower the melting point, improve strength, wettability, etc. Solders come to us from France, Germany and America. I'll tell you about domestic ones too.

Soldering iron for brazing aluminum

Soldering aluminum with a soldering iron should take into account the area of ​​the parts to be soldered. Aluminum, like copper, is a good conductor of heat, which means that more heat should come from the soldering iron than its soldered parts dissipate.

Soldering iron tip better to take with a larger area met mentions of serrated stingers. This is to make it easier to remove the oxide film under the oil layer. It is convenient to use such a sting - you do not need to cut the shavings.

Which is better - welding or brazing aluminum?

Disputes over the answer to aluminium Brazing process do not even think to subside. It turns out it all depends on your purpose. More precisely, the purpose of your connected parts.

Final Words

This is how I would formulate the answer to this question. It is clear that it is easier for a gas-welded craftsman to weld a radiator, and not to solder it, and vice versa - it is easier for a craftsman with a soldering iron to solder.