Soldering aluminum, as many experts rightly believe, is a rather difficult technological process to perform. Meanwhile, this opinion can be considered correct only in relation to those situations when they try to solder aluminum products using solders and fluxes that are used to join parts made of other metals: copper, steel, etc.
If you use a special flux for soldering aluminum, as well as the appropriate solder, then this technological process does not present any particular difficulties.
Features and principles of the process
The technological process of soldering is complicated by the low temperature value of the material melting . Parts will very quickly lose strength when heated, and the design will reduce stability when the temperature reaches 300 degrees. If you use low-melting solders, which consist of cadmium, bismuth, indium, tin, then they will be very difficult to come into contact with aluminum, and good strength will not be provided.
Metals that combine zinc have very good solubility . In this case, the soldered materials will be highly reliable. Before starting soldering, the material should be cleaned of oxides and dirt. For this purpose mechanical action is used. You can use a brush or use special fluxes that have a strong composition. Before starting the procedure, it is necessary to tin the areas that will be treated. If the coating is tin, the part will be protected from the formation of oxides.
To reliably solder aluminum products, you need to select the right heating tool. And the reliability of the connection also depends on the choice of alloy and flux for soldering aluminum.
What is the problem
The oxide film melts at a very high temperature. Its presence prevents the penetration of the solder melt into the base metal and disrupts the wetting of the soldering area.
Aluminum has a low melting point. It completely turns into a liquid state at 660℃. A change in the state of aggregation begins at a temperature of about 300 ℃. Most aluminum alloys contain metals that melt at as low as 500℃.
When high-temperature soldering, it is very easy to “overshoot” the small heating interval, which allows you to obtain a normal seam.
There is a high probability of overheating of the melting zone, as a result of which fragments of parts will turn into a liquid state. It should be remembered that soldering must be carried out by enveloping solid working areas of products with a molten mass of solder.
Soldering methods
Soldering of aluminum materials is carried out using an electric soldering iron, blowtorch or gas torch . There are several ways to solder aluminum:
- Using solder.
- With rosin.
- Using the electrochemical method.
With rosin
This option for soldering an aluminum surface must be used for small part sizes . The cleaned area must be coated with rosin and placed on sanding paper of medium grit. The wires are pressed on top with the tinned tip of a heated soldering iron. This action must be performed several times, after which the soldering procedure itself is performed. You can also use a rosin solution in diethyl ether.
In this option, the end of the soldering iron does not need to be removed from the embedded end, and you just need to add rosin on top. If you need to connect thin aluminum wires, then a soldering iron with a power of 50 W is suitable. If the thickness of the aluminum is approximately 1 mm, then the soldering iron must be selected at 100 W, and for parts thicker than 2 mm, preheating of the joint will be required.
Using solder
This method is very common and is often used in electrical engineering, car repair, and other products . Before starting the process, it is necessary to coat the material with an alloy, and then the tinned elements are connected. Parts that have been previously peeled are connected to each other and to other alloys and metals.
You can use light alloy solders that contain zinc, tin and cadmium. And also recently, refractory materials based on aluminum have been very actively used. Light alloy compounds are used because aluminum products can be soldered at temperatures up to 400 degrees. This will allow you not to spoil the properties of the material and maintain strength. Compositions with cadmium and tin will not allow for good contact, and they will also be susceptible to corrosion. Refractory materials do not have such disadvantages.
Electrochemical method
If you use the electrochemical method, then you will need a device for performing electroplating . This will result in copper plating of the surface. If there is no such device, then you will have to process the part yourself. To do this, you will need to sand the required surface and apply a few drops of copper sulfate. And only after that the negative pole of an independent power supply is connected to the product.
You can use a regular battery or accumulator, as well as any other electrical rectifier. A cleaned copper wire, which has a diameter of 1 mm and is located in an insulated stand, is connected to the positive terminal. When the electrolysis process occurs, copper begins to settle on the part, and only after that the area can be tinning and drying with a soldering iron. And after that you can easily solder the required tinned place.
Aluminum alloys with additives
High-temperature solder containing 66% pure aluminum, 28% copper and 6% silicon is effective for soldering. It was made in Russia. A significant concentration of the base metal, identical to the material of the working parts, increases solubility and penetration of the melt.
The base of the weld, which includes copper and aluminum, is strengthened by the presence of silicon. The connection formed using aluminum solder does not corrode and has good mechanical properties.
The addition of silicon increases the melting point of solders. Thus, a composition of 87% aluminum and 13% silicon melts at temperatures of about 600 ℃. This type of imported product goes on sale ready for use. Solder with flux is more expensive. The increased price is compensated by the high quality of the seam.
An American composite of 9 components gives excellent soldering results. The rods melt at a temperature of 347 ℃, increasing in volume by 10%. The resulting seam is distinguished by its ductility, which is 3 times higher than that of joints made from other alloys.
High-temperature soldering is carried out when working with massive parts made of aluminum or products made of alloys that melt only under strong heat. Heating is provided by gas burners operating on pure hydrocarbons or their mixtures with oxygen. You can use a regular soldering iron.
Solders, fluxes, materials
Tin can be used for soldering aluminum , but only in cases where there is a highly active flux, and the areas have been thoroughly cleaned. Tin compounds must be additionally coated with special compounds, since they exhibit poor strength and poor corrosion protection.
Very good solder joints can be achieved by using silicon, zinc, aluminum or copper solder . Such materials are produced by both domestic and foreign manufacturers. Russian brands of solders are produced under the name TsOP40. According to GOST, they contain 60% tin and 40% zinc, and there is also 34A solder. It contains 66% aluminum, 6% silicon and 28% copper. The composition will give good strength to the contact area and provide reliable corrosion resistance. Foreign compounds include HTS-2000. This product is very convenient to use.
Such alloys can be used with large-sized parts, as well as with high heat dissipation, if you use a heating pad or objects made of aluminum alloys with high-temperature melting. If you have never soldered objects before, then it is advisable to watch special training videos that will help answer many questions.
In addition to solders, it is also necessary to use special fluxes , which contain zinc, fluorine, ammonium burate, as well as triethanolamine and other elements . Popular domestic fluxes include F64, which has good chemical activity. Usually this product is used even without first cleaning the parts from the oxide film. You can also use 34A, which contains lithium, zinc and potassium chloride, as well as sodium fluoride.
Kastolin
Imported castolin consists only of aluminum and zinc. It has good fluidity, penetrating ability, and electrical conductivity.
Some inconvenience is caused by the impossibility of using this solder for parts with a magnesium content of more than 1.5% and products that are subsequently planned to be anodized.
Castolin sells a range of solders with a varied combination of components. After consultation, you can choose a remedy for specific conditions.
Preparation of material
To achieve a good quality connection, you need to use not only the right technologies, but also be able to properly prepare the surface to be treated . All dirt and oxide films must be removed. Mechanical processing is carried out using sandpaper or a metal brush, and sometimes a stainless steel mesh and a grinding machine are used. You can also use different acid solutions.
The surface must be degreased using solvent, acetone or gasoline. When an aluminum surface is cleaned, an oxide film immediately forms. However, its thickness will be lower than the original one, and therefore the soldering process will be easier.
Tools
If you need to connect aluminum products at home, then it is advisable to use an electric soldering iron. This is a universal device that very conveniently allows you to solder wires, repair small tubes and other elements. The adaptation requires a minimum amount of space. There must also be electricity in the house. If you need to repair a large-sized device, then use a gas torch for soldering aluminum, which uses butane, argon and propane. To solder objects at home, a standard blowtorch is suitable.
If gas burners are used, then it is necessary to constantly monitor the flame, which represents a balanced supply of gases and oxygen. If the correct gas mixture is present, the flame will be bright blue. A dim hue will indicate that there is excess oxygen.
Castolin AluFlam 190 – solder from France
The product is used as a filler rod for repairing aluminum parts and high-temperature brazing.
Technical characteristics of Castolin AluFlam 190 solder:
- It has high strength and exceptional capillary fluidity.
- Characterized by excellent electrical conductivity.
- The color matches many aluminum alloys.
Castolin AluFlam 190 is recommended for high strength connections:
- aluminum alloys with silicon;
- forged aluminum;
- sheets;
- pipelines.
It cannot be used for aluminum alloys containing more than 1.5% magnesium, and for parts that require subsequent anodizing.
Due to its ability to form a tough and strong weld, Castolin AluFlam 190 solder can be used in a wide variety of applications. It can be used to repair window frames and furniture, in the transport industry, to repair refrigeration equipment, gas lines, grilles, air conditioners and much more.
With the Castolin AluFlam 190 product, experts recommend using Castolin 190 Flux.
Aluminum soldering steps
Soldering aluminum objects is no different from joining other metal materials:
- First you need to clean and degrease the area of the future connection.
- Afterwards, all elements are installed in working position.
- Flux is applied to the required area and the product begins to be heated using a soldering iron or torch.
- When there is an increase in temperature, the solder bar melts; it must constantly touch the surface of the elements, thereby controlling the process.
It is necessary to remember that soldering should be done in a well-ventilated area , since during the heating process dangerous compounds are released.
If flux-free solder is used, then you need to know about some of the nuances of the work. To prevent the oxide film from interfering, you need to use the end of the rod to make scratching movements along the area of the element. Thus, the oxide integrity will be compromised and the solder will come into contact with the metal being processed.
The oxide layer can be destroyed in other ways. The area to be treated must be scratched with a wire brush or stainless steel rod.
To ensure maximum strength of the connection, it is necessary to treat the areas with tinning.
Safety precautions
Before you start working with a soldering iron, you should always first study the safety rules.
- You only need to work with the window open. Because you can get poisoned due to secretions during work.
- There should be nothing flammable around. If a soldering iron is dropped onto paper, for example, it can cause a fire.
- The device should be held exclusively by the special handle, since during operation it becomes very hot, which can lead to burns.
- Children should not be allowed near the soldering iron. The device should always be kept in a place that is difficult for the baby to reach.
- The device can only be lowered on a special stand during breaks between soldering. If the soldering iron is placed on a table, a fire may occur.
Follow these simple rules, and no problems will arise during operation.
To perform high-quality soldering of aluminum materials at home, it is necessary to fully comply with the technology. If you choose high-quality methods, solders, fluxes and materials, then the result will be positive.
