TIG (tungsten inert Gas) consists of that welding technique which uses Argon gas (Ar) in plasmatic state generated by the arc discharge between tungsten electrodes (W). This technique uses a pressure equal to or greater than atmospheric pressure for the gas, the process is carried out under inert atmosphere conditions, at 6000 K. This gas acquires electrical properties when it passes into the plasmatic state at certain conditions of intensity and voltage of electric current. The Argon gas used is of high purity with a contaminant content of less than 500 ppm. Tungsten is a gray metal with a high melting point of 3400-4000 °C. An important improvement in its properties is obtained when these electrodes Thorium oxide is added (Th), Zirconium (Zr), Lanthanum (The) or cerium (EC) in amounts between 0.15 – 4.2%. The electrodes used for this technique are classified according to the Standard ISO 6848.
Process description TIG welding
1.- General Start Conditions:
1.1.- Tungsten electrodes must be free of all types of contamination such as dust or grease, free of moisture, as well as the surfaces to be welded.
1.2.- Everything welding process always be carried out in environments free of direct air currents, the end of the electrode must not leave the protection ratio of the inert gas flow.
2.- Materials and Equipment
2.1.- Argon Gas. According to the supplier’s information, the high purity one with contaminants less than 500 ppm will be selected.
2.2.- Alternating current transformation equipment from 5 to 500 Amperes and voltage variation between 70 and 80 V of open circuit in the Arc.
2.3.- Tungsten Electrodes, (according to Norm ISO 6848. P.ejm.).
3.1.- The gas flow must cover the surface to be welded (bath) in a wide ratio so that it remains bright without opacities in the bead, otherwise it is deduced that the gas flow is insufficient. The gas flow must start before the ignition, and continue until after the extinction of the arc.
3.2.- Positioning of the Torch.
The torch must be kept slightly inclined (10 to 20°) from the vertical and directed from
so that the arc goes ahead of the molten pool.
After the arc has been prepared and the inert gas flow is maintained, the torch is held over the joint until a bright point appears, indicating that the metal of the piece has reached its melting point. This bright spot is increased in size when the welder makes small, circular movements with the torch depending on the displacement from right to left and adjusting the speed of advance and the extension of the bead according to the skill of the operator. This detail will be appreciated when maintaining a Bright and regular welding, without excess thickness.
4.- Verification. The quality of the welding cords is verified by the use of inspection plans and preferably approved techniques, making the respective corrections and their subsequent verification.
TIG Welding Applications
Its industrial application is extensive, being applied to all light metals such as Aluminum, Magnesium and alloys. Stainless steels (Chrome, Nickel, and alloys). Copper and its alloys. Lead, Silver, Gold, Carbon Steels, Metals different from each other, etc.
Video How to TIG Weld
How to TIG Weld Video 1