When tubes have to be welded, the GTAW (Gas Tungsten Arc Welding), also known as TIG (Tungsten Inert Gas) welding process offers numerous advantages: Compact, thin weld seam, full penetration and a clean process.
An important point of this procedure is that the weld seam is very high in quality, for two reasons: the purity of the weld as well as the surface finish. This becomes critical when a specific welding project demands such results for applications in industries such as semi-conductor, pharmaceutical, food & dairy and aerospace.
Advantages of GTAW
GTAW, or TIG welding, can be used for assembling production lines as well as on site repairs and other field applications. The main advantages of the TIG process relate to the high quality standard and the reliability of the weld: but this is not all.
- Depending on the final application, GTAW process can be used with or without filler wire.
- With GTAW, there is virtually no welding smoke or residue.
- Most metals can be welded with GTAW/TIG, even in the case of heterogeneous basic materials: stainless steel, titanium, magnesium, aluminium and copper.
- GTAW is a stable process and can be automated and applied in all welding positions.
- Defects of welding are extremely rare using orbital GTAW, and the welds are of a high quality.
Disadvantages of GTAW
GTAW equipment represents a higher investment compared to MIG/MAG welding for example, but the welding result is of a superior quality.
- GTAW equipment represents a higher investment on some occasions compared to other processes
- The process can take longer
- The required energy can be slightly higher
- GTAW can require a slightly cleaner environment
Materials and consumables.
TYPE OF POWER
When using the GTAW process, the most common power that is used is DC. Alternating current is used when welding aluminum.
Shielding gases protect the weld bead and the metal that is transferred through the arc from the ambient air, (which is 21% oxygen, 78% nitrogen, 1% other gases and humidity). The most common shielding gas is Argon. This gas helps with arc striking and is stable. Sometimes different gases are mixed depending on wall thickness, heat required and alloy.
In the past, tungsten-thoria electrodes have been frequently used for GTAW, but the thorium represents a risk in terms of radioactive isotopes. This can also present health hazards when grinding the tungsten. Today, welders use mostly cerium or lanthanum based tungsten electrodes in order to avoid risk of radioactivity.
No filler wire is necessary if you want to weld stainless steel with a wall thickness of less than .118”. A filler metal can necessary when required on certain exotic alloy and of course heavier wall applications.
Filler wire may be used when:
- Certain highly corrosive resistant alloys are being welded
- Thicker wall material requires a beveled joint
- Different types of alloys are being joined together
- If the structure of alloy is modified during the welding process
As you can see, GTAW or TIG welding is used when a very high quality of weld, with full penetration is required. This is the only way to obtain a high level of security and more guarantees during the root welding, where a perfect penetration is needed.
If you require more information, do not hesitate in reading our orbital TIG welding handbook, which will provide you with more information.