Gas Tungsten Arc Welding Process (GTAW)

Posted by Florida Gas Welding

TIGThe necessary heat for Gas Tungsten-Arc Welding (GTAW), or TIG, is produced by an electric arc maintained between a non consumable Tungsten electrode and the part to be welded. The heated weld zone, the molten metal, and the tungsten electrode are shielded from the atmosphere by a blanket of inert gas feed through the electrode holder. The GTAW process can produce temperatures of up to 35,000…. F. The GTAW torch brings heat only to the workpiece.
If filler metal is desired, it may be added manually like in oxy-acetylene welding or an automatic filler metal feeding system can be utilized.
The GTAW process has advantages over the other welding processes which in many cases make it more desirable to use.
Some of these advantages are:

A. Highly concentrated arc:
This permits pinpoint control of heat allowing a narrow heat affected zone. A high concentration of heat is an advantage when welding metals that possess high heat conductivity, such as aluminum and copper. Because of the highly concentrated arc, some safety precautions should be observed:

1. Unprotected skin is quickly “sunburned” by the arc rays. Eyes should be properly protected by the correct shade of lens.
Other workers in the area must be protected from stray glare or flash.
2. When welding in confined areas, such as inside tanks or containers, concentrations of ozone and nitrous oxides can easily reach an unsafe level. Precautions must be taken to ventilate these areas properly.

B. Inert gas shielding:
“Inert” means inactive or deficient in active chemical properties. The shielding gas serves only to blanket the weld and exclude the active properties in the surrounding air. It does not burn, and adds nothing to or takes anything from the metal. Inert gases like argon and helium do not chemically react or combine with other gases. They possess no odor and are transparent permitting the operator maximum visibility of the arc.

C. No flux or slag:
There is no requirement for flux with this process, therefore, there is no slag to obscure the operator’s vision of the puddle. The finished weld will not have slag to remove between passes. Entrapment of slag in multiple pass welds is not a problem.

D. No smoke or fumes:
The process itself does not produce smoke or injurious fumes. If the base metal contains coatings or elements such as lead or zinc that produce fumes, these must be contended with as in any fusion welding process on these materials. If the base metal contains oil, grease, paint or other contaminants, smoke and fumes will definitely be produced as the heat of the arc burns them
away. The base material should be cleaned to make the conditions most desirable.

E. No sparks or spatter:
In the GTAW process there is no transfer of metal across the arc. There are no molten globules of spatter to contend with and no sparks produced if the material being welded is free of contaminants. This is advantageous where spatter would create a problem around the weld or on adjoining parts.

In summary, GTAW welding is a clean process. It is desirable from an operator point-of-view because of the reasons outlined.
The operator must maintain good welding conditions by properly cleaning material, using clean filler metal, clean welding gloves, and keep oil, dirt and other contaminants away from the weld area. Cleanliness cannot be overemphasized, particularly on aluminum and magnesium. These metals are more susceptible to contaminants than are ferrous metals. Porosity in aluminum welds has been shown to be caused by hydrogen. Consequently, it is most important to eliminate any sources of hydrogen contamination such as moisture and hydrocarbons.

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