Tungsten Inert Gas Welding
The Definition of Tungsten Inert Gas Welding
Tungsten inert gas welding is a constant current drooping arc process. It is also known as TIG, gas tungsten arc welding – GTAW, wolfram inert gas – WIG, and under the trade names of argon arc and heli arc.
Type of Operation.
Usually manual, but can be mechanised.
Mode of Operation.
An arc is maintained between the end of a tungsten electrode and the work. The electrode is not consumed and the current is controlled by the power source setting. The operator must control the arc length and also add filler metal if needed to obtain the correct weld; consequently, a high degree of skill is needed for the best results. The arc is unstable at low currents. Special provision is made for starting (high frequency or surge injection) and for welding thin materials (pulse TIG)
Applications.
Aerospace materials.
Critical root runs in pipes.
General light applications.
Mechanised applications.
The advantages of TIG are that it gives the best degree of control and good weld metal composition.
The disadvantages of TIG welding are its slow speed and that it is more expensive than other welding systems.
The conventional machine for MMA and TIG is the constant current drooping characteristic. This refers to the volt-amp output characteristics. By using drooping an alteration in arc length gives a very small change in current, but with the flat type power source an attempted alteration in arc length (volts) will have little effect. Hence arc length remains constant but a significant change in current will result.
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