TIG (Tungsten Inert Gas) Welding
Also known as GTAW (Gas Tungsten Arc Welding).

Unlike MIG welding, TIG welding uses a non consumable tungsten electrode. The small intense arc is formed between the electrode and the parent metal being welded. A shielding gas is used to stabilize the arc and is supplied via the welding head. TIG welding can be done with or without a filler metal. If a filler metal is used it is applied separately as a stick. TIG welding requires a higher degree of dexterity to produce a good weld.

Tig welding is a popular choice of welding processes when high quality, precision welding is required.  This is because the arc formed is small and intense leading to highly localized heating. As the heated area is minimal the TIG is the preferred technique for more for welding thin sheet where distortion can be a problem.

Tig welding is often used for automated welding of piping.

Arc Initiation

In TIG welding an initial problem is initiating the arc. This can be achieved by shorting the tungsten electrode on the work piece. Only when the ‘short’ is broken will the arc flow. The risk here is that the tungsten electrode will stick to the surface and leave a tungsten inclusion in the weld. An alternative method to start the arc is to use an extremely high frequency which produces high voltage sparks for fractions of a second. The sparks ionize the atmosphere around the electrode which facilitates the formation of the arc.

Note the high frequencies used create high electromagnetic emissions which can interfere with electrical controls in the vicinity.

The shielding gases used in TIG welding are typically Argon and Argon/Hydrogen where hydrogen promotes arc formation and cleaner welds due to less surface oxidation also the arc tends to be hotter allowing faster welding speed. The downside of argon/hydrogen is the chance of porosity and cracking in carbon steels. Argon/helium mixtures give rise to greater heat generation and therefore deeper weld s but are more costly and make arc initiation more difficult.

TIG Advantages

• Can be used on all metals but is especially good for aluminum.
• The sharp and rigid tungsten tip allows for high precision, high quality welding.
• The small arc produced by TIG welding is ideal for welding thin materials.
• No weld spatter.
• No material is added to the weld unless it is required.
• Because the weld bead is smaller less grinding is required post operation.

TIG Disadvantages

• A greater degree of operator skill is required.
• A separate filler material must be used if additional material is required.
• The HF may cause electromagnetic interference to other nearby electrical equipment.
• As with tig requires a gas bottle – so not very portable.
• Lower metal deposition rates compared to MIG.
• TIG units tend to be more expensive than MIG units.