The opinion that it is very difficult to solder elements made of aluminum or alloys based on it is largely erroneous. Of course, if you use compounds designed for working with copper, brass or steel, it is almost impossible to get a positive result. Special solders for brazing aluminum will greatly simplify this process.
Features of aluminum and alloys based on it
The difficulties that arise when brazing aluminum are due to its specific features:
- high resistance of the oxide film to the surface;
- low melting point;
- high heat capacity.
According to the temperature indicators at which aluminum is brazed, two main methods are distinguished:
- low temperature in the range of 150-300 ° C (soft soldering);
- high temperature - 390-580⁰ (brazing).
Given the characteristics of metal, manufacturers have developed special solders and fluxes for brazing aluminum.
The benefits of soldering
Previously, special argon welding was used to connect aluminum parts. To carry out such work, expensive equipment was needed, and only a highly qualified specialist could use it. In addition, in the place of welding, the destruction of the metal occurred in depth.
Soldering aluminum with solders and fluxes is devoid of all the above disadvantages and has a number of advantages:
- Available parts are used to fasten parts.
- Work can be performed even by an unskilled performer, that is, they can be completed independently at home.
- The integrity and structure of the connected parts are not violated.
- With proper observance of the soldering technology, the mechanical strength of the joint is not inferior to the welds.
- Reheating allows you to easily change the relative position of parts and soldering.
High temperature aluminum brazing
In order to firmly connect sufficiently large aluminum elements, the so-called solid soldering is used. This will require:
- gas-burner;
- metal brush;
- solder.
The production algorithm is quite simple:
- In places of soldering, we carefully clean the parts using a steel brush.
- We heat the junction of parts using a gas burner to the melting point of the solder (for modern formulations this is usually 390-400 ° C).
- Firmly press the solder bar to the soldering place and apply it to the surface with reciprocating movements.
- We remove the oxide film under the molten solder with a steel brush.
- Let the parts cool naturally.
Brazing Solders
For a long time, only 34A solder was available to the Russian consumer. The main component of this composition is aluminum (up to 66%). The soldering temperature is 530-550 ° C. It is necessary to work with it extremely carefully so as not to melt or damage the fastened parts, because the melting of aluminum itself begins already at 660 ° C. In addition, when performing work on the recommendation of the manufacturer, the solder bar must be periodically dipped in flux F-34A.
The temperature of brazing aluminum solder HTS-2000 (US-made) is about 400 degrees. The connection of the elements is carried out without the use of flux. This greatly simplifies the process.
Another fairly popular and common flux-cored solder is the Swiss Castolin 192 FBK. The soldering temperature is slightly higher - 440 degrees. The presence of flux in the structure of the bar facilitates the removal of oxide film from the surface and provides reliable adhesion of the solder to aluminum.
Both of the above imported compounds are made on the basis of zinc, so the soldering place has high anti-corrosion properties.
Recently, foreign manufacturers have a worthy competitor - “Super A +” aluminum solder, which was developed and is now being manufactured in Novosibirsk. By its technical characteristics, it is in no way inferior to its Western counterparts. The brazing process is carried out at the same acceptable for metal 400 degrees. And there is no need to use flux. But the price for it is much lower (2-3 times) than its Western counterparts. Developers prudently do not publish the composition of the ingredients.
Low temperature aluminum brazing
Since soft soldering is usually carried out at a temperature in the range of 230-300 ° C, then for it you will need:
- electric soldering iron;
- solder for aluminum brazing;
- flux;
- convenient tools for stripping parts (metal brush, file or sandpaper).
Work order:
- We clean the connected parts in any mechanical way.
- We fix them in the right position.
- We apply a flux to the place of soldering (for example, with a brush).
- The tip of the (preheated) soldering iron and solder bar are abutted at the junction.
- The solder begins to melt. Advancing the soldering iron, solder the entire joint seam.
- Allow fastened parts to cool.
- Thoroughly clean the soldering area of flux residues (for example, a cloth dampened with alcohol or a rag).
Solders for soft soldering aluminum
For low-temperature brazing of aluminum, compositions from various manufacturers are currently used. Many successfully solder aluminum with Russian-made P250a solder. It is made on the basis of tin (80%). It also contains zinc (19.85%) and minor copper additives (0.15%). The low price and affordability of the acquisition provided him with sufficient popularity.
Swiss Solder Castolin 1827 for aluminum brazing is also quite common in our country. It consists of silver, cadmium and zinc. However, its price is much higher than the Russian counterpart. In addition, manufacturers convincingly recommend using it only with fluxes of their own production.
Aluminum Soldering Fluxes
Fluxes dissolve and remove the oxide film from the metal surface, and also contribute to better flowability of the molten solder, which ultimately affects the quality and strength of the connection. Therefore, they must be selected as carefully as solders for aluminum brazing.
Russian manufacturers (SmolTekhnoHim, Connector, Rexant, Zubr) offer two main types of liquid active fluxes: F-59A and F-61A. The letter index “A” in the marking means that their composition is specially designed for brazing aluminum, alloys based on it, as well as combined compounds with copper, steel and other metals.
Among the imported liquid fluxes for soft soldering, the Russian user is most famous for the Swiss Castolin AluTin 51. A carefully designed and well-balanced composition is suitable both for brazing aluminum elements and in combination with other metals.
All of the above fluxes are designed for low-temperature soldering (in the range from 150 to 300 degrees). The brazing of aluminum is carried out mainly either without the use of fluxes, or its components are built into the structure of the solder bar.
Finally
From the foregoing, we can make an unambiguous conclusion: the process of soldering aluminum elements is quite simple and accessible to everyone. Knowing which consumables to buy and which devices to use, you can both solder together aluminum electrical wires and repair the cracked oil pan of an automatic transmission.