Gas Tungsten Arc Welding
Table of Contents
Gas tungsten arc welding (GTAW) is a fusion welding process. Gas tungsten arc welding process is also known asTungsten Inert Gas (TIG) welding process. GTAW is another type of arc welding process in which the workpieces are joined by the heat obtained from an electric arc struck between a non-consumable tungsten electrode and the workpiece in the presence of an inert gas atmosphere.
A filler metal may be added if required, during the welding process.
Apparatus used in Gas Tungsten Arc Welding
- TIG equipment consists of a welding torch in which a non-consumable tungsten alloy electrode is held rigidly in the collet.
- The diameter of the electrode varies from 0.5 – 6.4 mm.
- TIG welding makes use of a shielding gas like argon or helium to protect the welding area from atmospheric gases such as oxygen and nitrogen, otherwise which may cause fusion defects and porosity in the weld metal.
- The shielding gas flow from the cylinder, through the passage in the electrode holder and then impinges on the workpiece.
- Pressure regulator and flow meters are used to regulate the pressure and flow of gas from the cylinder.
- Either AC or DC can be used to supply the required current.
Also read: Gas Metal Arc Welding (GMAW)
Procedure carried out during TIG welding
- The workpieces to be joined are cleaned to remove dirt, grease and other oxides chemically or mechanically to obtain a sound weld.
- The welding current and inert gas supply are turned ON.
- An arc is struck by touching the tip of the tungsten electrode with the workpiece and instantaneously the electrode is separated from the workpiece by a small distance of 1.5 – 3 mm such that the arc still remains between the electrode and the workpiece.
- The high intensity of the arc melts the workpiece metal forming a small molten metal pool.Filler metal in the form of a rod is added manually to the front end of the weld pool.
- The deposited filler metal fills and bonds the joint to form a single piece of metal
- The shielding gas is allowed to impinge on the solidifying weld pool for a few seconds even after the arc is extinguished (shut off)
- This will avoid atmospheric contamination of the solidifying metal thereby increasing the strength of the joint.
Advantages of Gas Tungsten Arc Welding
- Suitable for thin metals.
- Clear visibility of the arc provides the operator to have a greater control over the weld.
- Strong and high quality joints are obtained.
- No flux is used. Hence, no slag formation. This results in clean weld joints.
Disadvantages of Gas Tungsten Arc Welding
- TIG is the most difficult process compared to all the other welding processes. The welder must maintain short arc length, avoid contact between electrode and the workpiece and manually feed the filler metal with one hand while manipulating the torch with the other hand.
- Tungsten material when gets transferred into the molten metal contaminates the same leading to a hard and brittle joint.
- Skilled operator is required. Process is slower.
- Not suitable for thick metals.