Parts made of aluminum and its alloys are used in almost any industry. The use of this light metal with high thermal and electrical conductivity is the most common in household appliances. Therefore, when a malfunction occurs, it becomes necessary to weld aluminum structures and products in domestic conditions. It is almost impossible to carry out repair operations with this capricious metal without an apparatus for welding aluminum. And if earlier such work was available mainly in industrial conditions, now it is not difficult to do it in the home workshop.
Features of aluminum welding
The technology of the welding process of aluminum, like any other metal, has its own characteristics. Therefore, a novice welder needs to know and understand many of the characteristics of this metal. There is a wide range of special properties that aluminum has. Welding it involves the preliminary preparation of the material and the direct connection of parts.
In this case, you must take into account the properties of the metal:
- On the surface of aluminum there is always an oxide film, which significantly reduces the welding process. The melting point of the metal is 660 ℃, while the melting of the film occurs at 2000 ℃.
- In aluminum welding, metal drops, which are instantly coated with an oxide film, significantly interfere with the creation of a continuous seam. It prevents the formation of a high-quality seam in the open air. Therefore, the main condition for aluminum welding is the protection of the argon heating zone.
- Dissolved hydrogen, which is present in the composition of aluminum, escapes during welding into the atmosphere, which leads to the formation of crystalline cracks and pores.
- In the molten state, aluminum has a high fluidity, which makes it very difficult to create a weld pool. Therefore, when aluminum welding is required to arrange a good heat dissipation from the junction.
- Due to the high coefficient of linear expansion of the metal, a large shrinkage occurs during cooling.
- High thermal conductivity forces to increase the amount of current during welding, in order to reduce its duration.
- The mode and method of welding aluminum at home is difficult to set correctly because of the difficulty in determining the grade of the alloy.
Welding quality
To make a strong and reliable connection of aluminum parts, the welder must perform several basic technological steps:
- To remove the oxide film from the surface of the connection products. This operation can be performed both mechanically, cleaning the junction with a metal brush, and the chemical method using special solvents. But the most effective way will be to conduct aluminum welding with a semiautomatic device in a pulsed mode, which by means of instant heating of the metal ensures good removal of the oxide layer.
- Correctly carry out the heating of the metal surface in the desired temperature range. The main mistake of novice welders is overheating of the metal, which leads to burning of the junction.
- Significant linear shrinkage of aluminum during cooling can lead to deformation of the weld. Therefore, it is necessary to complete the welding process with less current. But at the beginning of the work it is necessary to supply a large current to ensure the penetration of the oxide film.
It is from the correct execution of all these operations that the quality connection of aluminum products depends.
Inverter welding technology
Subject to certain conditions, aluminum welding with an inverter is possible at home. For such work, special attention must be paid to consumables. The apparatus for welding aluminum has low requirements. To complete the connection you will need:
- Device for heating the electrodes. Performing roasting electrodes is a prerequisite and a prerequisite for joining aluminum parts. Most often, unsuccessful attempts at aluminum welding arise due to poor preparation of consumables.
- Special electrodes are used for welding metals with high thermal conductivity, which include aluminum.
- Inverter (apparatus for welding aluminum). Its level of performance when applied at home does not matter.
The process of joining aluminum parts must necessarily take place under the protection of inert gas.
The main stages of welding:
- Preparatory work includes cleaning the surface of the connected products and the mandatory preparation of electrodes.
- The welding process must be carried out carefully and slowly, strictly observing the desired penetration depth. After completion of the welding phase, the gas supply is not turned off for another five seconds.
Electrode Properties
The basis of the electrodes for welding aluminum includes pure metal, the mass of which is predominant, as well as additives that improve the joining process. The mechanical properties of welding devices are the main parameter by which they are selected for welding. The strength of the seam depends on this.
The main brands of electrodes for aluminum welding: OZA, OZA – 1, OZR – 2, OZANA – 2. All electrodes have the property of hygroscopicity, therefore, before operation, their mandatory drying at a temperature of 200 is required.
Semi-automatic connection
Semiautomatic welding of aluminum is necessarily performed under the protection of inert gas. Argon is used as such a gas. It is possible to conduct aluminum compound by a semiautomatic device without the use of inert gas, in the case of using a flux-cored flux-cored wire. Such a device is capable of spraying an iron-containing powder during heating. Such a cloud performs the function of protection, like argon.
The disadvantage of this method is the low quality of the weld, which significantly limits its use. The main task of the welder will be to decide which method to make the connection.
TIG Technology
When implementing this technology, non-meltable electrodes with tungsten content and an additive wire, which automatically fills the seam between the parts, are used. The use of such a process implies the use of alternating current mode and high-frequency ignition of the arc. In this case, the destruction of the oxide film occurs by cathodic sputtering at a current with reverse polarity.
MIG method
With MIG technology, the melting electrodes for aluminum welding are the additives themselves. This material enters the connection zone using a wire feed device.
Of course, it is very difficult to achieve high quality aluminum welding at home using this method, since it will require the use of a pulsed-arc apparatus. When welding, the torch must be directed at an angle of 10-20 degrees to the vertical, while the distance between the connection surface and the nozzle should be up to 10-15 mm.
Tips for gas welding aluminum
Before you start welding, you need to prepare all the materials and tools. A more reliable connection can be achieved with the help of an additional special rod. After thorough cleaning of the product surfaces, these places need to be treated with flux. This preparation method will reduce the effect of the oxide film and will allow welding of aluminum with a semiautomatic device in the highest quality.
Then the gas burner turns on and heats up to the optimum temperature. The next step will be to warm the welded joint to the melting point of the metal. During such heating, an additional rod is applied to the junction. During these operations, the metals melt and mix, resulting in a welded joint.
Remember that joining aluminum at home for a novice welder is considered a difficult job. Such problems mainly depend on the characteristics of the material used. The novice will have to be patient to gain the necessary experience in welding aluminum surfaces.