TIG WELDING

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A water-cooled non-consumable tungsten electrode shielded by inert gas is used in

a manual or mechanised process. A high frequency discharge or current surge is

used to ignite the arc as striking the arc may contaminate the expensive electrode.

Filler material, which could be waste pieces of the material being welded, may be

added to the weld pool for thicker plates. An AC is preferred over DC as it

(i) Stabilises the arc

(ii) Prevents overheating

Argon is normally used as the shielding gas for aluminium and steel welding while nitrogen or helium is used for copper welding. A ceramic disc directs the gas in a swirling flow, thus forming a shroud around the area. The process is normally used to weld thin sheets less than 6 mm. It is a clean process as the absence of flux results in no formation of slag or contaminating residue. This is beneficial if multi- pass runs have to be made. A skilled welder is required and high quality welds for stainless steels, nickel steels and aluminium alloys can be obtained.