Welding has been used for decades. The construction of virtually any building or structure requires the connection of metal structures. It can be metal beams, wire. Welding is widely used in industry. If several years ago we used large-sized equipment (transformers), then today inverters are increasingly used. Of great interest is the welding of aluminum parts. Not many people know how to cook aluminum with an inverter. It has its own characteristics associated with the properties of this metal.
The scheme of aluminum welding semiautomatic.
There are several types of welding: manual arc, gas, as well as using a semi-automatic or automatic. For aluminum, both manual welding and semi-automatic are suitable. In the latter case, a special device advances the welding wire into the work area, and the welder does the rest of the work. All this greatly improves the quality of the welded joint and increases the strength of the structure. It is necessary to consider in more detail the main stages of the work on the welding of aluminum products.
What is an inverter?
Scheme of the inverter device for welding.
To cook the inverter correctly, you need to know its features. An inverter is a device used to convert direct current into alternating current. This changes the frequency or voltage. Inverters can be used in combination with other devices or separately. Inverters are different, but they are all very compact. Today, almost all inverters are available as portable equipment. It is very convenient in the organization of welding. It is important that it is advisable to cook aluminum with an inverter only with the use of protective gas. Argon is used as the latter. Because of all this, it is recommended to purchase inverters specifically for argon-arc welding. This equipment has the following advantages:
- ensuring optimum burning of the welding arc;
- quick ignition;
- the formation of an even and high-quality seam;
- the ability to weld aluminum products of minimum thickness.
Chemical properties of aluminum.
To weld aluminum, you need to choose the right equipment (inverter). Today in stores there is a huge range of these goods. Virtually all units operate on a voltage of 220 V. The main technical characteristics include the limit of regulation of the strength of electric current, the presence or absence of possible sticking to the metal, dimensions, the presence of a rapid ignition of the arc.
The cost of the unit depends on its characteristics. The simplest inverter can be purchased for 6000-7000 rubles. In that case, if aluminum has to be welded infrequently, then it is best to borrow this unit. When buying equipment, you need to pay attention to the warranty period, the presence of a technical passport and its appearance.Back to table of contents
Features of welding aluminum products
Diagram of the process of aluminum welding semiautomatic.
Using the inverter, you need to cook very carefully. Experienced welders know that welding iron, cast iron and steel is much easier than aluminum. What caused such difficulties? The fact is that aluminum belongs to non-ferrous metals and has features.
Firstly, any aluminum product has a thin film on its surface. It is formed under natural conditions under the influence of air. When the metal is oxidized, this refractory film is very difficult to remove, which complicates the welding process.
In view of the foregoing, immediately before igniting the electric arc, it is necessary to prepare the surface of aluminum. This will require a metal brush or a solution of chemicals. With the help of mechanical or chemical impact can remove the film. It is important that for this you can use a special cored wire (flux). The latter dissolves and vaporizes the film.
Characteristic of aluminum.
Secondly, the complexity of welding aluminum lies in its physicochemical properties. It is a very soft and malleable metal, which, when exposed to high temperatures, loses its strength. Aluminum has a high fluidity, therefore, in order to avoid the flow of molten metal, it is advisable to carry out welding in a single layer. In this case, metal linings are often used.
Thirdly, aluminum products can easily be deformed when cooled, and cracks are formed. To avoid this, it is not necessary to place the welds close to each other, and also to add special additives to the welds, called modifiers.
Fourthly, another distinctive feature of this metal is that during operation, even at an arc temperature of several thousand degrees, it does not change its color. This makes it difficult to control the formation of the weld pool.Back to table of contents
Preparatory stage of work
The influence of gas components on the characteristics of the welding process.
To weld aluminum, it is necessary to prepare equipment, tools and materials. It must be remembered that the connection of aluminum products is carried out using protective argon. In addition, you will need a special prefix. It connects to the inverter. As for the electrodes, it is preferable to use tungsten-coated electrodes. They must be non-consumable. The peculiarity of such electrodes is that they contain alkali metal salts, which contribute to a better burning of the welding arc. Salts protect aluminum from oxidation. When choosing the diameter of the electrodes, the thickness of the metal is taken into account.
In addition to the apparatus and the electrodes, filler wire will be useful. The most common brands of wire are "AO", "AK". To weld aluminum, the diameter of the filler wire must be from 2 to 5 mm. To facilitate the welding work, you can use a semi-automatic. In this case, instead of conventional electrodes, welding wire is applied, which is fed to the metal to be welded using a special mechanism. Welding cannot be carried out without a power source. The electrical network must be operational. As for the strength of the current, it depends on the thickness of the metal and the diameter of the electrodes. It is possible to choose the optimum welding mode using the instructions for use attached to the inverter.Back to table of contents
Protective gas for aluminum welding
It is necessary to weld aluminum in the environment of protective gas. Today, carbon dioxide, helium, argon or their mixture is taken for these purposes. Argon is most suitable for aluminum. Welding using protective argon gas is carried out in a semi-automatic way. Argon refers to inert gases. This means that it prevents the oxidation of aluminum and prevents the negative effects of nitrogen and oxygen in the air on the metal. Argon itself does not enter into chemical interaction with other substances in the working area of the welder.
The supply of argon directly to the semi-automatic type inverter can be organized in two ways: by connecting the hose to the central gas pipeline or to cylinders. The latter contain several hundred liters of this gas at once. If welding is rarely done, then buying gas cylinders is not profitable. Of great importance is the fact that the mixture based on argon is preferable to pure argon. The gas mixture provides a higher melting rate, a reduction in metal spatter, a higher quality weld. In addition, energy is saved.Back to table of contents
The scheme of gas welding aluminum.
For optimal results, it is necessary to organize the correct supply of electric current. There is such a thing as polarity. In the presence of argon, alternating current is used with the inverter. In this case, the polarity should be reversed. This means that “+” is supplied to aluminum parts, and “-” to the equipment itself (burner). As for the direct current of reverse polarity, in the presence of non-consumable electrodes it is not served. There is one reason - incorrect distribution of thermal energy between the parts and the welding electrode.
The welder must remember that argon interferes with the normal ignition of the welding arc. If with the manual method of connecting parts it is enough to touch the surface of the product with an electrode, then in this situation it will not work. An oscillator is used for faster arc ignition. It contributes to the emergence of high-frequency pulses, with the result that the arc ignites quickly. The oscillator must be connected to the equipment along with the power supply. It is important that the current strength should exceed that in the welding of steel structures.Back to table of contents
Aluminum welding technology
With simple argon welding of aluminum, it is necessary to know that tungsten electrodes lose their properties during long-term storage and use. They can accumulate a large amount of tungsten oxide, from which the welding seam becomes less durable.
To remove them, it is advisable to sharpen the electrodes with a metal disk. Sharpening discs are universal tools, so they cannot be used for other purposes.
Aluminum welding should be carried out no later than 8 hours after mechanical or chemical cleaning of the edges and surface of aluminum parts.
Scheme of argon arc welding of aluminum.
Otherwise, a new film is formed.
After the mode is established and the integrity of the equipment is checked, the start button is activated. With the help of an oscillator, an arc is ignited. It burns directly between the aluminum and the electrode. In order to avoid getting a bad connection, it is recommended to test the welding mode on any other product. The electrode in the implementation of the work is located in the burner. Through the latter argon flows in the required volume. As for the filler material (wire), it can be fed into the working area automatically or manually. The burner nozzle does not need to be positioned on itself, it is necessary to drive the burner with one speed.
If aluminum has a thickness of less than 3 mm, then the seam is made single-layer. In this case, you will need a lining so that the metal does not leak out. With a part thickness of up to 6 mm, bevel edges can be omitted, and the seam can be two-sided. In the presence of aluminum of great thickness, up to four passes are made by a burner. If the work is done on semi-automatic inverters, aluminum wire can be used. Its optimum diameter is 1-2 mm, the current strength is not more than 300 A, argon consumption is from 300 to 600 l / h, and the speed of the wire is 150-160 m / h. When using tungsten electrodes, the current should be variable, and in the presence of melting ones, it should be constant.Back to table of contents
Effect of welding mode on weld quality
The highest value for obtaining the ideal weld has the mode of operation of the equipment. There is a direct link between the shape of the seam and the mode of operation. Firstly, the greater the current strength, the deeper the aluminum gets warm. This is of great importance in the presence of a large metal thickness. Secondly, the width of the weld does not depend on the magnitude of the current. What the seam will be, only the worker himself knows. Thirdly, the width of the welded joint is largely determined by the size (diameter) of the electrode. The same applies to the welding wire in the presence of a semi-automatic.
Fourth, an important condition for obtaining a strong connection is the speed of advancement of the electrode or wire. It should be big enough. The larger this value, the thinner and more aesthetically pleasing the seam will be. To make the seam wider, welders very often use oscillatory movements. This is especially true for manual welding. An important role is played by the argon feeding technique. When welding stops for a few seconds, it is not necessary to immediately stop feeding argon. It is advisable that he act for another 3-4 seconds. This will protect the electrode from oxidation and improve the weld.Back to table of contents
The scheme of technology of spot welding of aluminum.
Any welding work involves the protection of the worker and others from various harmful factors of the welding business. For this purpose, means of collective and individual protection are used. The first include the use of protective fences, non-flammable screens, ventilation systems. When using protective argon gas, welding is best done outdoors. During the work there is a high probability of electric shock. The welder is required to properly organize the grounding. Dielectric mats are often used.
To protect the respiratory system is desirable to use a mask. Any welding is a source of intense radiation that adversely affects the eyes. Because of all this, the worker must use a mask or shield. In addition, there must be overalls (costume, gloves, shoes), made of non-combustible materials. Equipment must be in good condition. Do not carry the welding inverter while holding the hoses. For this there is a handle built into the case.Back to table of contents
List of tools and materials
To organize such work you will need to purchase a set of tools. It includes an inverter, a nozzle, gas cylinders, an oscillator, electrodes or wire of the desired thickness, a metal brush for aluminum stripping, a hammer and a chisel to clean the product from the resulting slag. In addition, you need clothing, a source of electricity and an abrasive disc for cleaning tungsten electrodes. Argon should be enough for welding.
Thus, absolutely everyone can weld aluminum using an inverter. It is only necessary to know the device equipment and process technology. Aluminum is a metal that requires a certain approach. Aluminum welding is very common in the industry in the manufacture of various household appliances, so it is important to know all the nuances of the welding business. Receiving poor-quality welded joint indicates the wrong mode of operation. Do not forget that aluminum is better to weld in the presence of alternating current of reverse polarity. If you follow all the above rules, you can achieve high strength products.