TIG Welding stands for Tungsten Inert Gas and is a technique that’s known for using a non-consumable tungsten electrode along with an inert gas (usually argon). Tungsten is a rare, hard element that offers a high purity, high-quality weld.
In TIG welding, the heat is created by running an electric current through a tungsten electrode, creating an arc that is then used to melt a metal wire in order to create the weld pool.
TIG is most commonly used to weld stainless steel together, although other metals like magnesium, aluminum, copper and nickel can be welded using TIG.
TIG welding is the most widely used fusion welding process for aluminium.
During TIG welding, an arc is maintained between a tungsten electrode and the work piece in an inert atmosphere (Ar, He, or Ar-He mixture).
Depending on the weld preparation and the work-piece thickness, it is possible to work with or without a filler.
The filler can be introduced manually or half mechanically without current or only half mechanically under current.
The process itself can be manual, partly mechanised, fully mechanised or automatic.
The welding power source delivers direct or alternating current (partly with modulated or pulsed current).
Significance of flow meter –
The pressure of the gas contained in cylinders is reduced by pressure-reducing valves (Manometers for indicating cylinder pressure).
The amount of gas flowing in l/min is controlled via a regulating valve and indicated by the flow meter. In order to prevent any errors, the pressure-reducing valves have a colour code corresponding to the gas type (black for inert gases).
The type of gas used is also indicated in the manometer.
Effect of Current and Inert Gas
Both direct and alternating currents are used for welding aluminium.
- The weld pool and the weld forms can be regulated by controlling the current type and the polarity.
- The heat developed is highest when helium is used.
- In direct-current, straight-polarity welding (electrode is negative with respect to aluminium), the heating of the electrode is kept to a minimum but the cleaning action on the weld pool is also minimum. Helium is used as the shielding inert gas.
- The breakdown of the oxide film is a result of the thermal stressing, i.e., melting occurs.
- Because of its high melting point (ca. 2050 °C), the oxide layer cannot be melted using argon as the shielding gas.