METAL INERT GAS WELDING AND TUNGSTEN INERT GAS WELDING

      TUNGSTEN INERT GAS WELDING (TIG)

CHARACTERISTICS IN BRIEF

• It is known as GAS TUNGSTEN ARC WELDING (GTAW).
• Also called Argon arc welding.
• The region of weld is surrounded by inert gas. No atmospheric contact, hence no contamination.
• In this welding power source is connected to electrode and the work material.
• Arc is produced between the electrode and work piece.
• Coolant is supplied to avoid the melting due to high temperature.
• Such welding is used for highly reactive materials. Stainless steel, aluminum are some examples.
• For thin metals filler is not used.

 DEMERITS

• Overall production is costlier.
• If tungsten particle adhere in weld pool then it may make weld brittle.

 METAL INERT GAS WELDING (MIG)

The various components of metal inert arc welding are:-
1) Power source
2) Electrodes
3) Weld torch
4) Shield gas
5) Weld pool.

The power source used is constant voltage ranging from 25 volt to 150 volt is needed and direct current is preferred. Sometimes alternating current can also used. Direct current has a advantage of eliminating arc blow. Depending on material thickness current is applied during welding. For 5 mm thick metals current of approx 200 ampere is required. Similarly for thickness approximately 10 mm current of nearly 750 ampere will be required.
The electrode used in metal inert gas welding is made up of similar material as that work piece. The diameter entirely depends on the current which is dependent on the thickness of material. Greater the thickness of work piece, greater will be the current required and greater will be the diameter required.
There are various ways to transfer metal in the welding pool.

1) By short circuiting
2) Spraying
3) Pulsation
4) Globular transfer

It is a type of metal joining process in which electric arc is maintained above the work piece through welding gun. The wire electrode also called filler wire or consumable electrode is fed continuously. At high temperature the work piece melts and also the wire electrode melts which adds to pool of molten metal. During the welding process gas shield is also provided by the welding gun along with consumable electrode. The shielding gas may be carbon dioxide which provides protective surrounding around the weld pool to avoid contamination of atmosphere and gases like oxygen and nitrogen. Desirable amount of shield gas is induced through welding gun depending on type of operation, work piece geometry, current and type of shield gas and current.