How to braze aluminum with a gas torch

How to solder aluminum at home with a soldering iron

Aluminum is one of the most common metals. It is found not only in manufacturing, but also in the home. And sometimes there is a need to connect some parts of aluminum or its alloys. But to do it without special equipment is not so easy. Therefore, we should consider options on how to solder aluminum with a soldering iron at home, and what it takes.

aluminum, torch

Aluminium is one of the most difficult metals to solder

Soldering techniques

The problem when using aluminum conductors is their rapid oxidation. The oxide film has a significant obstacle to the passage of electric current at joining. To do this, the strands of aluminum wires are soldered. You can solder aluminum wires in a junction box using a soldering iron or a gas torch. The soldering iron is more difficult to use because you can’t heat it to the exact temperature you need. And for aluminum, overheating is just as unacceptable as underheating.

Metal has a high thermal conductivity, and the insulation in a large area away from the soldering point can just melt.

It is easier to adjust heating temperature with a gas torch, but it takes too long to prepare the surface. Nevertheless, you will need to use the torch if you want to solder any solid parts to each other. In any case, when soldering aluminum wires, you need to prepare them.

Fluxes for aluminum brazing

Fluxes have a high activity, so after soldering they need to be washed with a solution of water with alkali. Baking soda works well as an alkali. After caustic soda the joint place should be washed with clean water. Protect your respiratory system from flux vapors. They can irritate the mucous membranes and enter the bloodstream. The most common ones need to be considered each separately.


Rosin is the most popular flux. It is used in joining various metals. Works on aluminium only in the absence of air, so it is rarely used. time is spent working with rosin, less efficiency. This flux is not for professionals, can perform soldering, but the quality of the connection is not strong.

Powder flux

Aluminium is soldered with a gas torch and powder fluxes are used. It is not recommended to add oxygen to the flame, it reduces the effectiveness of the flux. The most common fluxes:

F-34A is an active flux containing 50% potassium chloride, 32% lithium chloride, 10% sodium fluoride and 8% zinc chloride. Compound is used with solders that contain chemical additives. It is hygroscopic and water-soluble.

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Borax powder, melting at 700 ° C, has solubility in water, washed with aqueous citric acid solution. Low cost.

Acetylsalicylic acid is found in the form of aspirin tablets. Emits harmful vapors when heated with a soldering iron that burns the nose, eyes, and respiratory organs.

Solder oil consists of paraffin, ammonium chloride and zinc, deionized water. Good for soldering preheated and tinned parts. After soldering aluminum parts it is recommended to wash off flux residuals, otherwise it will cause corrosion of the metal.

Liquid flux

Liquid flux is applied to the soldering point as a thin layer. Evaporates quickly releasing scalding vapors in the soldering iron. Fluoride F-64 contains fluorides, tetraethylammonium, corrosion inhibitors and dionized water. Well breaks oxide film and helps solder large aluminum workpieces. Used for soldering copper, aluminum, galvanized iron and other metals.

F-61 consists of triethanolamine, ammonium fluoroborate and zinc fluoroborate. Used for tinning and brazing of aluminum alloys at temperatures up to 250°C. Castolin Alutin 51 L consists of cadmium, lead and 32% tin. Works most effectively at temperatures above 160°C.

Any of the above fluxes helps solder aluminum pan, aluminum billets of different sizes, to join by soldering method duralumin, duralumin (dural) billets.

How soldering is accomplished

A specialized solder is used for aluminum, which is able to resist the protective action of the oxide film on the metal surface.

Several brands can be used as such solder, such as HTS-2000 or Castolin-192. Structurally the solder tube is a fusible metal tube (zinc compounds are used), in the center of which a special flux for aluminum soldering is poured.

It is this flux that is used to dissolve the thin oxide film on the surface of aluminum. In order to properly conduct the soldering, it is necessary to ensure that the soldered surfaces are at a temperature of 480 ° C.

At lower temperatures, the solder metal will not be able to react with the oxide and break it down into its components, thus allowing the solder material to provide good contact with the surface.

In order to give the elements of the structure the required temperature, an ordinary gas burner is used. Both a portable and a stationary gas torch can be used for this purpose.

You can get solder that allows you to solder aluminum at specialized stores that make and sell a variety of copper tubing and radiator products. This could be, for example, a service center for repair of refrigerators, etc.

How to “Weld” Aluminum Without a Welder

Sometimes finding the right solder can take quite a bit of time, because the problem is quite specific and not everywhere you can find the information of interest. As a last resort, you can use any marketplace. This can be, for example, the same network Avito.

But the best (if you can wait, of course) is to go to Aliexpress. There you can order any solder for aluminum of interest at an attractive price and fairly fast delivery time.

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For example, the purchase of solder for aluminum products can be made here: Go to the site

It is desirable before you start soldering, especially if it is done for the first time, to conduct a training soldering holes. To do this, make a few holes in any unnecessary tube, which should be soldered.

The soldering point should be well heated

So do not choose to heat soldered parts of the torch low power or frankly low-quality goods.

The flame of such torches will be too narrow, it will not warm up the edges of the seam, and the soldering will last very long, because the solder will constantly try to drain from the soldering point, will collect in balls, will reluctantly stick to the metal, etc.д.

Making soldering of aluminum parts with low-powered torches is very problematic, so it is better to use a burner on a cylinder

Its wide flame allows you to heat not only the soldered joints, but also the metal at some distance from them in one go.

Soldering aluminum at home with a torch, solder

Soldering aluminum is a difficult process at home. The difficulty can be explained by the properties of the metal, which makes it difficult to join individual parts made of aluminum with other substances. Solder aluminum with specially designed techniques to ensure the quality of soldering. The experience of the craftsman who joins aluminum parts by soldering is important.

Heating sources

A propane or butane gas torch is mainly used as an element with which to heat up the large aluminum parts to be joined and melt the solder. If you decide to solder aluminum products with your own hands in the conditions of the home workshop, you can also use an ordinary soldering lamp.

A gas soldering lamp is handy to use

When performing the heating, it is necessary to be very careful not to melt the parts to be joined. To do this, touch the surface of the parts as often as possible to check the beginning of its melting. This is the indication that the operating temperature has been reached.

When heating parts and solder before beginning soldering, you must also watch the flame of the gas torch: the mixture of gas and oxygen that forms it must be balanced. This must be done because the balanced gas mixture actively heats the metal, but does not have a serious oxidizing effect. The fact that the gas mixture is balanced is evidenced by the bright blue color of the flame, which has a small size. If the burner flame is too small and has a pale blue color, it is an indication that there is too much oxygen in the gas mixture.

Soldering aluminum in the home

The process of joining aluminum and its alloys by soldering is a difficult process, because the material does not have the best properties for it. Nevertheless, it is actively used in the industrial sphere and parts made of it that need to be repaired are found in various areas. Soldering aluminum at home is complicated by the fact that it is impossible to provide the same technical basis as in industrial processing. At the same time, aluminum itself is well machined, so it is not very difficult to prepare the metal.

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Almost the same methods are used here, and the appropriate brazing alloys for aluminum are chosen. Sometimes improvised means are used as flux, such as metal chips from aluminum, rosin and other. They don’t always help to the same extent as factory options, but they do provide an improved connection. At home most often soldered wires, various housings of household appliances, aluminum cookware and other parts. Despite the fact that soldering aluminum soldering iron at home does not require full compliance with technological requirements, they all improve the quality of the connection, so it is required to meet them as much as possible.

Soldering aluminum

Aluminum is among those metals that are actively used in industry. It is amenable to mechanical processing, has relatively low weight and high strength, which makes it very popular in industry. At the same time soldering aluminum is quite difficult, as the metal has not predisposing properties. Not only is solder for aluminum soldering required here, but also special flux and the use of special techniques that should provide the best welding properties. Soldering of aluminum wires and resonant voltage stabilizers is most common.

Naturally, brazing aluminum will not give the same high quality as welding aluminum, but it is practically not required in such cases, since the parts almost do not have to face high mechanical loads. Depending on the different applications of this process, there are several varieties of solders, which facilitate obtaining certain properties. Their selection largely determines the quality of the process, because here it is necessary to choose the right temperature, so that the metal did not lose the properties of strength due to heating, and was able to take substances from the additive material, as has a low solubility in relation to other elements. Soldering of aluminum is performed in accordance with GOST 21930-76.

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