What Is TIG Welding? Details on Use and Safety
One of the most recognizable terms used in welding is “TIG welding”, which the AWS A3 standard defines as “a nonstandard term for gas tungsten arc welding.” TIG is actually slang for Gas Tungsten Arc Welding (GTAW), but it is used so often that it is at least acknowledged by the standard as a (non-standard) term1. In this article we will use GTAW and TIG interchangeably, following the notation in the A3 standard.
What Is TIG Welding?
GTAW, or TIG welding, is an arc-welding process that uses a non-consumable tungsten electrode to generate the heat and resulting molten metal pool for the welder to add filler material. The electrode, molten pool and the consumable filler material are shielded in a continuous flow of inert gas to keep the point of welding free of contaminants. There can be no foreign material or moisture present in the area being welded.
Important Advice About TIG Welding Safety
The temperatures produced during TIG welding vary, based on power input, shielding gas used, arc length and flow rate, but the molten pool can reach up to 19,000 Kelvin (over 33,000 degrees F). For some perspective on that heat level, the temperature of the sun's surface is about 10,000 degrees Fahrenheit (5,600 Celsius or 5,810 Kelvin). With these temperatures, safety is absolutely critical. The TIG Welder would be smart to follow all safety guidelines as established by the American Welding Society in the Safety in Welding, Cutting, and Allied Processes guide (ANSI Z49.1:2021).
What Is TIG Welding Used For?
This high temperature is useful for welding metals with extremely high melting points and will therefore be able to generate high quality welds in virtually any material. This is very useful in aerospace and naval application, where welds will need to be extremely strong and withstand extreme temperature ranges.
Temperature and weld control can be altered depending on the base material and the welding components selected. The welder must be very careful in identifying the base metal correctly, as this will indicate which tungsten electrode, shielding gas and filler material to use.
TIG welding is useful in welding carbon steel, stainless steel, galvanized steel and aluminum of various thicknesses, depending on shape (pipe, plate and sheet metal), and environment in which the finished product will be used2.
What Variables Must The Welder Consider?
Since TIG welding is often used for joining steel plate and piping for load-bearing structures, the welder will always want to maximize the strength and integrity of their welds by ensuring that they have properly selected the right filler material for the weld joint, the appropriate gas for shielding, and the correct electrode tip for process. Here is what the welder must match together for the weld being planned:
Tungsten Electrodes Used In TIG Welding3
There are at least 8 kinds of tungsten electrodes commercially available for use in TIG welding, and each one is identified by a standardized assigned color. These colors are important because they inform the welder what the tungsten electrode contains3.
- GREEN: A pure tungsten electrode is color-coded green and contains pure tungsten. It is often used for welding magnesium and aluminum with alternating current.
- RED: A tungsten electrode contains 2% thorium and is usually used in direct current (DC) welding. This type of electrode can withstand higher voltages than pure Tungsten, and can be used to weld titanium, which has a melting point of 3,034 degrees F. This electrode is called a Red Thoriated Electrode, and has the drawback of being radioactive, so extra precautions must be taken when using thoriated electrodes.
- YELLOW: The yellow-tipped thoriated tungsten electrode has the exact same properties as the red thoriated electrode, except that it contains 1% thorium instead of the red electrode’s 2% composition. The same safety considerations should be followed due to the radioactivity of the thoriated electrode.
- PURPLE: The Purple E3 Tungsten electrode mixes the non-radioactive pure tungsten properties with additional oxides that allows the positive performance traits of thoriated tungsten (easier ignition and sustained stable arc) but without the radioactivity factor.
- ORANGE: Known as Ceriated tungsten, these electrodes contain at least 97.3% tungsten, with the remaining percentage being composed of Cerium. This allows for use with low current welders, and can be used to weld steels, nickel and titanium. Its is generally considered not radioactive, but certain isotopes of cerium might contain trace amounts of thorium, which is radioactive.
- GOLD: The gold tipped electrodes indicate that the tungsten is lanthanated. This means that the tungsten contains a small amount of lanthanum oxide (La2O3). Lanthana is a non-radioactive rare earth element and is useful in TIG welding due to arc stability and durability.
- BROWN: Zirconiated tungsten electrodes contain less than 1% zirconium, with the balance being pure tungsten. It is considered a very stable alloy to work with and is used exclusively in AC welding. It is completely incompatible with DC welding.
- GRAY: These are tungsten electrodes that contain rare earth oxides. Useful in both AC and DC welding. While rare earth impregnated tungsten electrodes can be counted on for durability and a stable arc, the welder should pay close attention to the actual composition of the rod for compatibility with welding type (AC or DC).
Shielding Gases Used In TIG Welding
Shielding gases for TIG welding are usually Helium and Argon. When TIG welding was first developed, Helium was the shielding gas of choice, which gave GTAW its original name: Heliarc Welding. Argon took over as the principle gas due to the cost of helium. Other gases can be used as shields in TIG welding, including nitrogen and hydrogen, the latter used only with particular base metals4.
Filler Material Used In TIG Welding
Selecting the right filler material for TIG welding depends upon the composition of the two pieces being joined together. For this purpose, we will first cover tig welding similar metals, such as joining stainless steel (316L) to another piece of the same composition, then the filler material should be 316L filler material5.
When joining dissimilar metals, the filler material must be metallurgically compatible with both base metals; this is why the welder must be sure of the composition of the base metals being joined, as the filler material must be compatible with both materials.
The Welding Environment
Where is the welding going to take place? It would be nice if all TIG welding could happen in a specialized shop with optimized ventilation and nothing nearby that might be an obstacle, but the real world usually doesn’t offer ideal situations for welders to work in. The welder needs to prepare for this by inspecting the location and ensuring that the welding can be safely accomplished with proper shielding, ventilation and personal safety equipment. Extra care should be taken when working with thoriated tungsten, to minimize contact with radiative materials.
The TIG Welding Takeaway
TIG Welding works with extreme temperatures, and like any kind of welding, it can present serious risk to the careless welder. With the same interest and care you dedicate to your TIG welding craft, you will want to dedicate double the effort in understanding safety to person and property. Do not cut corners of any kind. Welding is both science and art form, and it is for serious and careful people.
Sources:
1 “What’s Wrong with MIG and TIG?“ from https://www.aws.org/magazines-and-media/inspection-trends/it-aug-23-editorial/#:~:text=The%20AWS%20A3%20standard%20defines%20TIG Published in August 2023. Retrieved on November 19, 2024.
2 “American Welding Society Procedures” from https://pubs.aws.org/t/procedures Retrieved on November 19, 2024.
3 “How to Choose the Right Tungsten for TIG Welding and What Tungsten is Best for Your Setup” from https://bakersgas.com/blogs/tig/tig-tuesday-how-to-choose-the-right-tungsten-for-tig-welding Retrieved on November 20, 2024.
4 “Shielding gas recommendations for MIG and TIG welding” from https://www.alleima.com/en/technical-center/shielding-the-weld/#:~:text=The%20normal%20gas%20for%20TIG Retrieved on November 20, 2024.
5 “Selection of Filler Metal Alloy for Welding Process“ from https://www.alleima.com/en/technical-center/welding-guide/#:~:text=Selection%20of%20Filler%20Metal Retrieved on November 20, 2024.