|
|
|
TIG - Arc welding through the tig process
|
1. Process description
The arc welding process under a protective gas protector with a non-consumable electrode, also called TIG (Tungsten Inert gas) uses an electric arc as the energy source and this is established between the non-consumable electrode and the actual part being welded, while an inert gas protects the molten pool. When filler material is used, it is supplied by means of rods as in oxyacetylene welding.
During this process, the TIG torch must be connected to the negative pole (-) and the ground clip must be connected to the positive pole (+).
2. Aplications
The TIG process can be employed in the welding of all materials, including aluminium, magnesium and materials that are sensitive to oxidation, such as titanium.
It is a mainly manual process, with a lower deposition rate compared to other processes and for this reason it usually employed in applications that require a visually perfect finish.
The possibility of welding one material to another will depend on the characteristics of the available equipment. The TIG process can be used with both DC and AC power supplies. The choice of power type and polarity is made according to the material to be welded.
3. Selecting the type of power (AC / DC)
TIG direct current (DC)
Any SOLTER INVERTER equipment can supply direct current (DC), and all are able to weld perfectly using any one of them with the TIG procedure. These units are mainly employed in the welding of STEEL AND STAINLESS STEEL materials.
With conventional INVERTER equipment, the arc is primed by contact with the part to be welded and the gas opening is manual. There are also professional SOLTER TIG models where the arc is primed without contact and by high frequency (HF) and the gas is automatically opened by an electro-valve.
TIG alternating current (AC)
Specific SOLTER INVERTER units provide alternating current (AC) TIG welding because they must also maintain the high frequency (HF) in continuous operation in order to maintain the arc during the process. This type of equipment usually provides both types of power, AC and DC, which means it is possible to weld ALUMINIUM and TITANIUM… with AC, in addition to those described in the section above with DC.
4. Welding equipment
The basic equipment for TIG welding consists of a power source, a TIG torch fitted with a non-consumable tungsten electrode, a ground clip and a bottle of inert gas (almost always 100% ARGON).
4.1. TIG torch
This conducts the current and the protective gas to the welding area. The tungsten electrode, which carries and maintains the current up to the welding zone, is firmly held in place by a clip housed inside the electrode-carrier body.
The protective gas reaches the welding area through a ceramic nozzle that is fitted to the electrode-carrier head. This nozzle directs and distributes the protective gas over the welding zone.
4.2. Ground clip
The correct connection of the ground clip is of extreme importance. The location of the corresponding cable is especially relevant in the welding process. A poorly fastened cable cannot provide a constant good electrical connection and could easily heat up, leading to a break in the circuit and consequent loss of arc.
The ground clip contact area must be thoroughly clean and free from any substances that could prevent good contact, such as paint, varnish, oils....
5. Welding parameters
5.1. Electrode
The normally employed electrodes are made of tungsten with thorium. For guideline purposes, the welding currents should be as follows:
Electrode
|
Welding current
|
1,6 mm.
|
3-35 Amp.
|
2,0 mm.
|
30-100 Amp.
|
2,4 mm.
|
100-160 Amp.
|
6.2. Preparing electrodes for TIG welding
Special attention should be paid to the preparation of the electrode tip.
Angle will vary with the welding current; the table below provides recommended values:
Angle
|
Welding current
|
30º
|
5-30 Amp.
|
60-90º
|
30-120 Amp.
|
90-120º
|
12-160 Amp.
|
6. Devices
In equipment that can be employed for TIG welding, arc priming may be obtained in three different ways:
Scratch priming:
The arc is established by scratching the part to be welded on the tungsten electrode.
LIFT-ARC priming:
The arc is established when the part to be welded is touched with the tungsten electrode and then withdrawn. There is no need to scratch the part which prevents possible contamination of the tungsten electrode.
High frequency (HF) priming:
This method establishes the arc automatically without any need for contact between the tungsten electrode and the part being welded. It completely avoids the effects of electrode contamination.
Electro-válvula:
Los equipos TIG equipados con este dispositivo, suministran gas sobre el baño de fusión una vez se aprieta de gatillo de la antorcha. Este gas se corta automáticamente en el momento que se deja de apretar dicho gatillo.
Rampa de bajada:
Nos permite regular el tiempo durante el cual la corriente de soldadura ira disminuyendo al final de proceso. Este dispositivo elimina la aparición el cráter al final del cordón.
Post-gas:
Nos permite regular también el tiempo que continuará saliendo gas una ves terminado el cordón. Este dispositivo se utiliza para proteger el baño de fusión una vez extinguido el arco.
|
|
