The need for welding work often arises not only in production, but also in everyday life. Welding of aluminum products and structures at home is carried out quite often, despite the occurrence of some difficulties. The difficulties are due, first of all, to the characteristics that this material has. the conditions necessary for working with aluminum .
However, situations arise when it is necessary to repair aluminum products. In such cases, the work is performed at home, by the contractor’s independent efforts. Therefore, in this article we will look at the main features and nuances of aluminum welding.
Application of aluminum
The widespread use of aluminum products lies primarily in the fact that it is a light metal. Aluminum is widely used in electrical engineering because it has excellent electrical conductivity.
For household needs, pots, cans, colanders, and mugs are made from this metal. Pure aluminum is used to produce foil used for electrolytic capacitors. It can also be used in the production of radiators.
However, soldering this metal can cause a lot of problems. This is explained by the fact that upon slight interaction with air, the surface of aluminum is covered with a thin but hard oxide film. It protects aluminum from further oxidation, but during the soldering process it creates a difficult barrier to overcome.
There are several methods to solve this problem, for example, soldering with rosin, but the best results are obtained by using fluxes specially designed for this.
DIY electrodes for aluminum
Aluminum electrodes for welding are metal rods coated with coating. The coating protects the metal from oxidation and improves the quality of the weld. They are practically not used in large workshops and factories, since their efficiency is not enough to perform large volumes of work. But such electrodes are widely used by home craftsmen.
A carbon electrode is often used to weld aluminum. In this article we will tell you everything you need to know about aluminum rods and explain in detail how to make your own welding electrodes.
What electrodes to use for aluminum welding
Are you interested in what aluminum electrodes exist for electric arc welding and shielding gases? Let's talk about industrial and homemade rods!
Soldering problems
The melting point of aluminum does not exceed 660 degrees. The consequence of this is the use, for economic reasons, of welding machines that do not have too much power.
However, there is an oxide film on the surface of aluminum that must be removed before starting the welding process. But to melt it requires heating to a temperature of 2000 degrees. When this value is reached, not only the oxide film will be destroyed, but also the metal itself, which will lead to a deterioration in the quality of the welded joint. In addition, the oxide film can be restored after it has melted. Due to the stability of the oxide film, which has weak adhesion to solder, conventional solder has difficulty sticking to the surface of the part.
Aluminum soldering flux solves this problem. When applied to the welding area, it will block the passage of air into this area, which will lead to a weakening of the negative effects of the oxide film. Compared to other metals, such as iron and zinc, aluminum is more active - a cleaned part can instantly become covered again with an oxide film. Therefore, flux intended for aluminum parts is also required to act quickly.
Active flux for low-temperature soldering of aluminum will quickly dissolve the oxide film on the surface of products that interferes with the normal spreading of solder. In addition, zinc is added to the solder intended for joining aluminum products, which has the ability to dissolve well in aluminum.
A connection based on solder containing zinc has greater strength. By combining the appropriate solder and a universal flux for soldering aluminum, you can obtain a high-quality connection without much difficulty.
Welding aluminum at home: methods
Household welding of aluminum can be carried out not only by the standard MMA method, but also by other methods. We will consider the most popular and accessible technologies for home craftsmen below.
Welding aluminum with a gas torch
This method involves using gas energy as a temperature force to melt the metal. Gas is a more reliable means of protecting the work area from exposure to atmospheric air than electrode coating. This method is one of the most accessible for welding aluminum at home. The equipment and filler materials are of reasonable cost, and the process is quite simple.
Semi-automatic (DC MIG)
Despite the high efficiency of semi-automatic welding (DC MIG), this method is used much less frequently. This is explained by the fairly significant cost of equipment. Pulsing equipment produces a high voltage surge that destroys the film on the metal surface. Each particle of the molten electrode rod is driven into the weld pool. The modern unit performs spot welding, providing a high-quality, reliable, durable and aesthetically attractive connection. Some features :
- it is necessary to carry out welding only with current with reverse polarity;
to avoid wire getting stuck in the feed mechanism, it is necessary to use special tips marked “Al” or standard models, but with an increased diameter;- aluminum rod can create loops, to avoid this you should purchase a special feeder with four rollers, a small sleeve and a Teflon liner;
- you need to maintain an accelerated wire feed rate, which will avoid frequent tip changes.
In order to save money, some craftsmen have learned to modify standard types of semi-automatic machines to work with aluminum.
Argon (AC TIG)
The consumables are tungsten electrodes (rods with a diameter of 1.6-5 mm), capable of withstanding temperatures of 3000°C, and filler wire with a cross-section of 1.6-4 mm. They provide high quality seams. Gases are used to protect the welding zone: argon or helium. Thus, the performer will also need a gas cylinder. Manufacturers produce compact tanks specifically for household welding, the volume of which is sufficient for minor repairs.
The arc is powered from an alternating current source. Argon arc welding is a fairly expensive method for working with aluminum. In addition, the welding process is characterized by technical complexity. Therefore, TIG welding is used quite rarely at home.
Inverter and coated consumable electrode
A seam made with the OZANA-2 electrode.
The simplest and most convenient way is to weld aluminum with an inverter using consumable electrodes of the following brands: UANA, OZANA, OZA. Special coated rods and corresponding equipment allow you to weld products from both pure aluminum and alloys of this material. The work is performed with direct current of reverse polarity. The current value is calculated as follows: per 1 mm. a current of 25 A should be accepted.
Additional means that provide a high level of protection are a gas cylinder and hoses. The burner is used as a tool for heating metal. This method is used when the connection does not have special requirements for strength and reliability. Equipment and consumables are quite low in cost.
Features of the substance
Active flux for soldering aluminum has significant differences from similar substances used to join products made of steel, brass and copper, just as the properties of these metals themselves differ. The flux composition contains substances that can easily dissolve the oxide film on the surface of aluminum. For soldering aluminum products, fluxes of various numbers are used.
The simplest are fluxes No. 8 and 9, however, their activity is not too great compared to those that include fluorine compounds. The choice is made based on the characteristics of a particular job. There are fluxes that are used for welding joints of parts without prior preparation. The most common type of flux is F-64.
The composition of the flux for aluminum soldering, number F-64, contributes to its increased activity, which makes it possible to successfully clean even uncleaned surfaces from the oxide film. The solution is colorless or light yellow.
Preparation of aluminum parts for welding
Due to the specific properties of aluminum, its preparation before welding is of key importance to the final result.
Particular attention should be paid to the location (edges of the product) for the planned weld. Mainly cleaning is performed in order to get rid of the oxide film.
Sequence of preparation:
- Cleaning and degreasing the material from plaque of any origin . This is done with acetone, solvent, or, less commonly, aviation gasoline.
- Cutting edges is necessary if their thickness exceeds 4 mm when using standard electrodes.
- Removing the oxide film . The tool is selected according to the thickness of the aluminum part. Usually a file, milling cutter or metal brush is used.
Solders used
When welding products made of aluminum, it is recommended to use solders from the tin-lead group. The highest quality connection can be obtained if you use a type of solder that contains elements such as silicon, zinc, and copper. The addition of additives significantly improves the quality of the solder - they lower its melting point, increase wettability, and make it more durable.
These types of solders are produced by domestic industry and foreign manufacturers. Tin-lead solders have the lowest melting point. One of the most common brands of solder for aluminum welding is HTS-2000. Experienced welders say that HTS-2000 solder should only be used with flux to obtain a high-quality connection.
Good substances in this area also include solder from the French company Castolin 192FBK, as well as Castolin 1827 solder, used when joining parts made of aluminum and copper. The domestic analogue of HTS-2000 is SUPER A+ solder, manufactured in Novosibirsk, which is used in conjunction with SUPER FA flux.
Welding aluminum with an electrode at home
Welding aluminum at home with electrodes involves several different methods.
The most common method is inverter welding, analyzed above.
Also, when working with consumable electrodes, welding transformer . The technology is practically no different from steel welding, but the seam may not be of the highest quality.
In addition to using tungsten electrodes in argon arc welding, carbon rods . The shielding gas supplied from the burner can be argon, acetylene, propane or others. It all depends on whether the performer has them. The welder will also need a powdered flux that prevents the electrode from sticking and removes the oxide film. The arc power source can be a welding inverter or a transformer. In some cases, to stabilize the working process, a magnetic field is required, which is created by the solenoid.
Preparing metal for welding
Regardless of the welding method used, it is imperative to carry out preparatory procedures for the working surface: Filler materials and product edges must be cleaned of dirt, oil and grease .
Chemical treatment includes several procedures:
- degreasing the surface with a solvent: white spirit, acetone, aviation gasoline or any other;
- etching using concentrated alkali, duration – 2 minutes;
- the metal must be washed with cold water;
- passivation with 30% nitric acid solution for two minutes;
- rinsing with water again;
- drying.
If aluminum welding is carried out with uncoated electrodes, then edge cutting is carried out when working with products with a thickness of more than 4 mm. The use of consumables with coating involves cutting edges when connecting parts to walls with a thickness of over 20 mm. The ends of thin aluminum sheets (no more than 1.5 mm) must be beaded.
Using a file, a brush with stainless steel/steel bristles (in the picture) or sandpaper, the surface to be welded is cleaned.
Welding process
After preparing the product, the welder can begin the main work.
The process of welding aluminum and its alloys includes several important stages:
- heating the product to a temperature of 150°C;
- setting the welding machine to the required mode;
- excitation of the welding arc , depending on the welding method, can be carried out by contact and non-contact methods;
- creation of a weld pool , the formation of which occurs in a few seconds (the required time is approximately equal to the thickness of the part in millimeters); a spot of molten aluminum with a mirror surface should appear in the heating zone;
- after the formation of the pool, you can begin to supply the additive and perform welding;
- welding is carried out with an arc of 2-6 mm, using direct current of reverse polarity.
Video
Great demo video from Zeller that gives an idea of the process.
Safety precautions
Welding various aluminum structures involves providing protection for the performer. To do this, you need to use special equipment : a mask, mittens, rubberized shoes, asbestos or tarpaulin, sheet iron.
It is necessary to isolate all elements of the electrical circuit.
Do not carry out work in rooms where flammable objects .
It is necessary to have ventilation in the room to avoid gas poisoning.
Safety precautions MUST be followed as there is an increased risk of injury when working at home.
Flux F-61
An option such as F-61 flux is worthy of special attention. It refers to a type of active flux for removing oxides from the surface of aluminum products intended for soldering. At the same time, it improves the spreading process of liquid solder. Flux F-61A can also be used when joining aluminum and aluminum-based alloys with copper and steel products. What sets it apart from the entire group of similar elements is that it is made on the basis of fluoroborates.
Flux F-61A produced by REXANT is a low-temperature flux. It is used when soldering aluminum using solders belonging to the tin-lead group. The temperature regime is in the range of 150-320 degrees.
F-61A flux has the following composition:
- triethanolamine - 82 percent;
- zinc fluoroborate - 10 percent;
- ammonium fluoroborate - 8 percent.
The flux is packaged in dark glass bottles containing 30 milliliters of substance each. The dimensions of the bottle are on average 35x20 with a height of 76 millimeters. The weight of the bottle is about 0.03 kilograms. For ease of use, the bottle is equipped with a dropper, which makes it possible to use the flux in doses.
The flux complies with the requirements of the regulatory document OST 4 GO.033.200. Its price is affordable. Flux F-61A is supplied with instructions for use, which must be carefully studied before use. In particular, it specifies safety precautions during welding.
If flux gets on the welder’s skin, you should immediately wash the area with soapy water and wipe dry with a clean cloth. Bottles with flux must be stored in such a way that they cannot fall into the hands of children. The guaranteed shelf life is one year. After the process is completed, the remaining flux is removed using a cloth moistened with water or alcohol.
Making a welding electrode
From time to time we need a welding machine. We learned exactly how you can make a simple welding machine at home in one of our previous materials. However, it is simply impossible to use a welding machine without electrodes, so in addition to the previous material, we present to your attention a lesson on making a homemade welding electrode.
Let's get acquainted with the electrode manufacturing process by watching the video
Liquid glass is not as difficult to find as it might seem at first glance. This glass is sold in almost any hardware store. Everything is clear with the materials, and this means that we can begin the process of manufacturing our electrode.
First we need to grind the chalk into a fine fraction. To do this, put pieces of chalk in a blender and turn it on.
Next, we align our wire and rod mode. At this stage, you need to try to make the rods even.
Now we spread liquid glass on the rods. To do this, you just need to place the rods on a flat surface, wet the brush in liquid glass and apply it to the pieces of wire.
The next thing is to pour chalk crushed in a blender onto our rod.
Now we are trying to roll everything out evenly.
Our electrode is almost ready. At this stage we just need to wait for it to dry. After our electrode has hardened and the liquid glass on it has thickened, we need to calcinate it. To do this, you need to place the electrode in a regular oven.
Turn on the oven and set the temperature to 100 degrees Celsius. Place the electrodes in the oven for half an hour. This time is enough for the liquid glass to harden.
Externally, a homemade electrode differs from a factory one. The first difference can be called its color. In addition, it crumbles a little, but this feature does not interfere with the welding process. The author's test of the homemade electrode shows that it copes with its task perfectly.
Self-production
It is possible to make flux for soldering aluminum with your own hands. Substances that have good solubility and antioxidant properties are suitable for production. When preparing flux for aluminum with your own hands, alcohol, acids, and oils are used as a basis.
The simplest flux can be prepared by dissolving a tablet of acetylsalicylic acid, best known as aspirin, in water. The tablet should be dissolved until the sediment disappears. You can also use citric acid granules.
A good flux can be obtained by dissolving rosin in ethyl alcohol. Since it dissolves slowly, it should be crushed as thoroughly as possible. To complete dissolution, the solution should be left for some time. This process can be accelerated by placing the solution in a glass jar and heating it in a water bath to a temperature of 80 degrees.
The advantage of flux obtained from rosin dissolved in alcohol is its neutrality, which allows its residues not to be washed off after the soldering process is completed. It is allowed to dissolve not in ethyl alcohol, but in glycerin. This flux will be thicker and more convenient to use.
Selecting consumables for welding
To cook aluminum with an inverter without argon, electrodes made of a material similar in composition are used. When heated, their coating creates a gaseous environment that prevents the penetration of air into the welding zone. The best domestic brands were recognized as OZA, OZR, OZANA. Foreign-made analogues OK 96.20, OK 96.40, Kobatek-213 are better in quality, but are more expensive.
Argon arc welding is performed with non-consumable tungsten electrodes. To create a seam, filler wire with a diameter of 2 to 5 mm is used. Popular brands AO, AD, AK contain a lot of magnesium.
To weld aluminum with a semi-automatic inverter, filler wire with a diameter of 0.8 to 1 mm is used in 0.5 kg coils. The most popular brands are ER 4043 and ER 5356, made from an alloy of silicon and aluminum. Sv-AK 5 and Sv-AMg made of aluminum with magnesium are used less frequently.
Welding without argon
Many owners are interested in how to weld aluminum without argon. This requires special consumables - for example, Nobitec 412 electrodes or TBW Harasil NC12 rod. Prepare a large number of electrodes in advance, as they are consumed 3 times faster than what happens when welding steel products.
It is advisable to preheat the aluminum to a temperature of 150-200 degrees Celsius. Welding should be done with a short arc at a current of 70-100 A. The electrode should be positioned at an angle of 90 degrees. After finishing the work, the scale is beaten off with a hammer, and the weld seam is cleaned with a brush.
This method is suitable for those who do not know how to weld with argon or do not have equipment for gas welding. In this case, the strength of the connection will be no worse than with argon welding. Despite the fact that specialized electrodes are quite expensive, the final cost of the connection is less than when welding with argon.
Useful tips
- Welding must be done with direct current with reverse polarity. Is it possible to weld aluminum with alternating current? It is possible, provided that the oscillator and ballast rheostat are used.
- Aluminum cooks best at a temperature of 18 – 22 degrees Celsius and humidity within 70%
- Surfaces must not be cleaned with sandpaper or abrasives.
- Aluminum alloys should be strengthened by cold hardening before electric welding. In industrial conditions, the aluminum coating can be up to 40% of its volume; in domestic conditions, a much thinner layer should be formed.
- To avoid hot cracks, the surfaces must be heated before welding.
- To learn how to weld without craters, first practice on unnecessary pieces of metal. Without turning off the arc, it is necessary to weld in the opposite direction. When welding the crater, form a kind of dome over it, and during cooling, a crack will not form in this place.
- The ejection speed of aluminum wire when using a semi-automatic machine should be 15-20% higher than that of analogues made of ferrous metals.
- Before welding aluminum with an electrode, do not forget to calcinate the consumable material, since it is very hygroscopic.
- If the arc breaks when welding with a consumable electrode, then the next seam should overlap the previous one by about 1 cm. Before continuing work, remove the slag crust from the electrode and crater.
