A Quick Guide to TIG Welding
TIG (Tungsten Inert Gas) welding is an arc welding process in which a non-consumable tungsten electrode delivers the current to the welding arc. The tungsten electrode and the weld area are cooled and protected from oxidation and other particulate contamination by an inert gas like helium or argon. Like oxy-acetylene welding, TIG welding requires a filler metal to be used for reinforcement or build-up. Some welds, however, do not require a filler metal. TIG welding is technically known as GTAW, or Gas Tungsten Arc Welding, but most welders still call it TIG or heliarc.
The chemical and physical properties of tungsten make it ideal for applications that require an extremely high melting point, or conducting electricity at high temperatures. The tungsten electrode allows the arc to maintain temperatures of up to 6000℃. The metal’s high melting point and exceptional electrical conductivity keeps the electrode from melting due to the heat. Compared to steel, which has a tensile strength of 36000 PSI, titanium has a tensile strength of up to 500000 PSI.
GTAW requires the welder to use both hands when welding. Unlike other arc welding processes, the way the arc is created and filler metal is added in TIG welding is different. One hand holds the torch that creates the arc, while the other adds the filler metal into the weld joint. Since TIG welding requires both hands, it is one of the most difficult welding processes to learn. It is also one of the most versatile and sought after.
TIG welding is often utilised when the project requires a high-quality and aesthetically pleasing weld. While GTAW is one of the most complex welding processes, evaluating the quality of a TIG weld can be as simple as examining the bead’s characteristics. A simple visual inspection will reveal much about the quality of the weld. A cursory inspection is easier to perform and costs less compared to other more intricate forms of inspection.
Basics of TIG Welding
GTAW requires that a few conditions be met to ensure a proper weld. Here are some of the basics.
- The base metal and filler material must be clean and free of other pollutants like oil, rust and paint. Dirty and tainted material must be cleaned before welding. Use a tool like a wire brush or a grinder if necessary.
- The work area must be properly ventilated and well-lit. If proper ventilation cannot be assured, the welder must be equipped with a dedicated oxygen supply and/or carbon welding masks.
- The power source must have a reliable current control that should be kept in the low range. This is required to manage the arc’s stability.
The aim of the bead is to ensure strong and stable bonding with the base metal with a satisfactory fusion. A good weld looks clean, with no burn marks and other imperfections, and should be the same colour as the base metal. The width of the bead should have a consistent profile all throughout. The edges of the groove should transition smoothly into the base without the appearance of grooves.
Shielding gas is required to protect the weld from atmospheric contamination. Shielding gases are typically inert gases like argon and helium. Do to their chemical properties, helium and argon have no effect on the traits of the weld area. The gases do not inflict any deleterious changes on the weld. What you see is what you get.
In some cases, a mixture of different gases is used. The most typical are: argon and nitrogen, argon and hydrogen, and argon and helium. The third mixture is mostly used on dense metals to ensure a deeper penetration.
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