TIG Welding of Aluminum
TIG (or Tungsten Inert Gas) welding, also known as Gas Tungsten Arc Welding (or GTAW), is an arc welding process, undertaken by a specialized aluminum welding shop, and makes use of a non-consumable tungsten electrode (or a non-filler metal electrode) in order to produce a weld.
Pure argon gas is the preferred inert shielding gas for welding aliminium materials with a thickness of up to a ½ inch. Above this thickness, between 25% to 75% of helium is added in order to make the arc hotter, resulting in deeper penetration.An inert shielding gas (either argon or helium) is used to protect the weld area of the aluminum from atmospheric contamination. In some cases, a filler metal is also used, though it is not needed for autogenous welds – welds where heat is used and filler rods are not required .
A constant-current welding power supply is employed to produce energy, which is, in turn, is conducted across the arc. This conduction of the arc takes place through a column of metal vapors (plasma) and highly ionized gas.
Most frequently associated with aluminium, TIG welding is used to join metals that have a smaller thickness. Though not the only method that can be used in welding aluminum, it is the preferred option when it comes the lighter gauges.
Aluminum welding shops will often use an alternating current in the TIG welding process, but a direct current can also be used. The type of current used to TIG weld aluminum will depend on the properties desired by the customer for the final product, though Alternating Current is the preferred method.
For TIG welding, the work area is cleaned and sometimes preheated to a temperature between 175°C (347°F) and 200°C (392°F). Doing this will help to increase the travel speed and improve penetration. In order for welding to be possible, the thin oxide layer, which forms when aluminum is exposed to air, also has to be removed.
An AC (or alternating current) has a self-cleaning effect that removes the thin layer of oxide formed the moment aluminum is exposed to air. When this type of current is used for welding, two types of electrodes are over the use of thoriated electrodes:
- pure tungsten electrodes
- zirconiated tungsten electrodes
The reason behind this is that when thoriated electrodes are used, it is more likely to ‘spew’ or ‘spit’ electrode particles across the welding arc and into the weld itself. When using alternating currents for welding, blunt electrode tips are preferred.
During this TIG welding process, pure argon shielding gas should be used when working with thinner pieces and materials, while the introduction of helium will allow for a greater penetration when it comes to thicker pieces and materials.
Do note however that the use of helium can result in a difficulty of starting an arc.
Advantages of TIG weld aluminum
Noted below are some of the advantages associated with TIG weld aluminum:
TIG or GTAW can be used in the welding of a wide range of materials, from stainless steel to non-ferrous metals, including aluminum alloys, copper alloys and magnesium alloys.
This welding process is effective for welding thin sections as well as more delicate work pieces. TIG welders also has the added benefit of being able to control the heat and amperage relatively easily.
The welds produced by TIG is of high quality and also produces a clean appearance. Mechanically strong, this process has also become a popular choice in the automotive industry for aluminum. Able to produce a weld that needs no finishing (leaving it as-is with no further grinding needed) it is aesthetically pleasing and eliminates the time used and problems associated with grinding.
Disadvantages associated with TIG and GTAW includes the fact that is a slower and more expensive welding method. It also often restricted to the welding of horizontal and flat surfaces.
Back to Main Page: Aluminum Fabricators
Further Suggested Reading:
- Aluminum Grades for Sheet Fabrication and Chinese Equivalents
- Aluminum Sheet Fabrication
- Aluminum Tube Fabrication
- Anodizing Aluminum Fabrication
- Tolerances in Aluminum Fabrication
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