For welding non-ferrous metals it is necessary to apply special technologies. It is possible to weld parts from copper, stainless steel, aluminum, etc., using argon-arc welding. The cost of such services from specialists is quite high, so in order to save money, arc welding can be done with your own hands.
Scheme of argon arc welding with non-consumable electrode.
Welding non-ferrous metals requires some skills. Beginners can be recommended to first practice with more simple examples.
Argon welding technology
The technology of arc welding in argon medium combines in itself some principles of arc (electric) and gas welding. In the process, a welding arc is used. The actions of the welder are about the same as in conventional gas welding.
Electric arc is an element of welding equipment that provides heating and melting of the surfaces being welded. Argon is used during welding due to the fact that when interacting with oxygen, oxides of alloyed steels and non-ferrous metals are formed. Bubbles form in the seams, causing the joint to become fragile. Aluminum begins to burn in an oxygen environment. Argon is used to prevent the interaction of oxygen with the welded metal surfaces, as well as the effect of various impurities in the air on the metal to be welded.
Connection diagram of the welding torch to the power source.
Argon easily displaces oxygen from the welding site due to the fact that it is 38% heavier than air. The supply of argon must be started 20 seconds before the arc starts to work in order to prepare the welding zone. The feed is stopped approximately 10 seconds after welding. Chemical reactions involving argon and welded metals or gases that are near the welding zone do not occur. However, you should consider the peculiarity of this inert gas. If welding is performed in reverse polarity, then electrons are split off from the gas atoms, due to which the argon medium is completely converted into an electrically conductive plasma.
Melting and non-consumable electrode can be used for this type of welding. In the latter case, tungsten is used. It is the most refractory metal. The material of manufacture and the optimal diameter of the electrode used depends on the material being processed.
Argon arc welding is known in 3 varieties:
- manual with non-consumable electrode (AHR);
- automatic with tungsten electrode (AAD);
- automatic with consumable electrode (AADP).
The scheme of the welding electrode.
The main element in the design of an argon arc welding torch is a tungsten electrode. Such electrodes do not melt. Its edge should protrude 2–5 mm relative to the tip of the burner. An electrode of any diameter can be installed on a special place in the burner thanks to a special holder inside its structure.
A ceramic nozzle is worn around the main element. It will supply argon to the welding site. In addition, during the work used filler wire from the same material that is welded.Back to table of contents
The procedure for performing arc welding with argon
First of all, the surfaces that will be welded must be cleaned. From them should be removed any dirt, grease, oxides. You can use a mechanical or chemical method of purification.
On the prepared part is fed "mass". With this action begins the process of arc welding without the use of argon. When processing parts of a very small size, you can apply it to a work desk made of iron or a bath. The filler wire does not need to be included in the electrical circuit, it must be fed separately.
The torch should be in the welder’s right hand and the filler wire in the left. The burner is equipped with a button that turns on the flow of argon and current. First, the supply of argon is turned on, and after 20 seconds - the supply of current. The strength of the welding current supplied depends on the metal being welded. The burner with current should be located at a distance of about 2 mm from the metal surface of the workpiece.
Table selection of current for welding.
In the interval from the surface to be welded to the tip of the electrode, an electric arc is formed. The result is the melting of the filler wire and the edges of the parts that are welded.
The distance from the tip of the electrode to the metal surface should be minimal. This will contribute to the formation of a short arc. The metal will melt deeper in a short arc. With the shortest arc, the welding seam will be as thin and aesthetic as possible. A large arc increases stress and reduces the quality of the weld.
The burner should be guided smoothly and slowly along the seam. Do not allow transverse movements. At the same time, filler wire is gradually supplied as required. The quality and appearance of the weld will depend entirely on the accuracy of the welder’s actions.
If the filler wire is fed in sharply, the metal will be sprayed. For accurate wire feeding, some dexterity in welding is required. It is more convenient to place it in front of the burner. Crossing the filler wire is also prohibited. The wire should form an angle with the surface of the welded part.
It is strictly forbidden to touch the tip of the electrode to the metal surface of the parts to cause ignition of the arc. This is due to the following reasons:
- When touched, a spark will appear that will not allow to ionize the gap between the surfaces of the parts and the tip of the electrode sufficiently. This is due to the high argon ionization potential.
- At the electrode appear dirt after touching the surfaces of parts.
When using a tungsten electrode, it is possible to start an arc due to an oscillator connected in parallel to a power source. The oscillator provides high-frequency high-voltage pulses to the electrode. Due to this, the arc gap is ionized. The oscillator converts the standard 220 V and 55 Hz of the power grid to 2000-6000 V with a frequency of 150-500 kHz. Due to this, the electrode is easily ignited.Back to table of contents
Welding in an argon environment using a conventional arc welding machine will not work. For this you need additional specialized equipment. Must stock the following:
The scheme of the movements of the electrode during welding.
- Transformer. You can use an ordinary device designed for arc welding. However, one should take into account the technological features of the process when choosing the appropriate power of the device.
- Power contractor. Provides welding voltage to the torch.
- A device for adjusting the blowing time with argon. It is necessary to start supplying gas in advance, and stop its supply a little later than turn off the burner. The regulator is needed to ensure this delay.
- Welding torch
- Argon in a cylinder that is equipped with a gearbox.
- Non-consumable tungsten electrodes.
- Additional transformer. It will provide electricity for switching devices.
- Rectifier. It will provide power to the switching devices with direct current with a voltage of 24 V.
- Electrogas valve. When powered by alternating current 220 V, constant - 24 V.
- On and off relay for contractor and oscillator.
- Inductive capacitive filter. This equipment allows you to protect the welding transformer from high-voltage pulses that the oscillator sends.
- Ammeter to measure the strength of the welding current.
- Car battery. You can even use faulty. It will be connected in series to the electrical circuit. This will reduce the DC component of the current, the occurrence of which always accompanies welding with alternating current.
- Protective glasses.
On the basis of these devices it is possible to assemble a device for welding with argon. Produced and ready-made equipment, which can be purchased in case there is no desire to mess with the assembly of the device.Back to table of contents
Selection of the optimal welding mode
The quality of welding is determined by the correct selection of the welding mode.
The polarity and direction of current used depend on the characteristics and qualities of the material being processed. To work with the main steels and alloys applied direct current with direct polarity. To weld non-ferrous metals, alternating current is used, the polarity must be reversed. This mode will ensure that the oxide film will break down faster. 70% of the heat generated by direct current falls on the anode, and on the cathode - the remaining 30%. In order to effectively melt metal surfaces and not to overheat the electrode, direct polarity is established.
Thus, argon welding with your own hands can be performed by almost every craftsman who has arc welding apparatus with some welding skills. For some metals only this welding method can be applied. It ensures the creation of high-quality welding seam of high strength. This is especially important if it is necessary to weld thin metal with access to parts only from one side.