All you need to know about the process that has revolutionized welding techniques and related portable systems for over 50 years.
Like most of the inventions that have radically changed human progress, making it possible to take significant steps forward in technological evolution at all levels, the TIG welding method also has its origins in the military field.
During the Second World War the American aviation industry faced the problem of the weight of the cells of fighter aircraft, and above all the possible ways to further increase the speed and maneuverability of the same.
Both large bombers and fighter planes, in fact, despite being made with the new aluminum alloys, much lighter than steel sheets, were in any case weighed down by the high number of rivets necessary to seal the various components. the structure of the aircraft.
The need arose for a new type of high quality welded joint capable of offering greater sealing and productivity than the traditional coated electrode process. Thus it was that the welding methods were developed that the AWS, or the American Welding Society, defined with the abbreviations SAW and GTAW.
The various types
The abbreviation SAW ( Submerged Arc Welding ), or submerged arc, indicates a particular continuous wire arc welding process where the bath is kept under slag protection; that is, this type of welding exploits the slag produced by the same, which, deposited on the bath, acts as a thermal insulator, keeping the high temperature produced inside it, thus increasing the speed of execution and therefore productivity.
The GTAW ( Gas Tungsten Arc Welding ) method was then developed from the SAW method , the definition of which was subsequently simplified and internationalized with the abbreviation TIG ( Tungsten Inert Gas ). In this process, the weld pool, instead of from slag deposits, is protected by a “jacket” of inert gas. Apart from the increase in productivity, therefore, TIG welding also offers an increase in the quality of the joint, as the weld pool is also protected from slag and, consequently, from potential inclusions of the same in the joint.
The equipment needed to perform TIG welding
Before understanding how it works, you must first know how the welding system commonly known as a TIG welding machine is composed. In principle, in fact, even the best TIG welding machine is not dissimilar from a classic traditional welding system, since the primary components of the equipment are the same; the only differences lie in the type of torch used and in the presence of the gas reducer and any internal housing for the coil of wire.
The latter is “possible” in the sense that not all TIG welding procedures are necessarily carried out with continuous wire, and there are TIG welders whose torch is made to house the specific tungsten electrode required for this method.
What changes from model to model, however, is the power level of the system, which defines the intended use of the welding machine.
A typical TIG welding system, therefore, consists of the current generator, the torch, the inert gas cylinder, necessary to provide the protective “jacket” for the bathroom, and any metal filler rods, in case of required their use. So let’s take a closer look at the different components.
The power generator
As mentioned above, the current generator is not dissimilar to that of the other welders, but being equipped with an Inverter they are much lighter than the old systems with the transformer.
The power of the output current, expressed in Ampere, varies according to the type of generator and its intended use; those designed for domestic and hobby use, for example, have an output current that does not exceed 150-170 A, while systems intended for professional use reach up to 200-300 A and more, depending on the model.
The TIG torch
The TIG welding torch is made in the shape of a gun and is itself composed of various elements. In reality it is nothing more than a support for the infusible tungsten electrode, both the cables for the power supply and an interchangeable ceramic nozzle are connected to this support, to allow the use of electrodes of different diameters.
The main role of the nozzle, of course, is that of dispenser for the shielding gas, which is emitted in such a way as to surround the electrode when the welding arc is fired. TIG torches for continuous wire welding, on the other hand, have a sliding mechanism for the wire instead of the electrode holder.
The gas cylinders
To protect the weld pool, different types of inert gas are used depending on the case: argon, helium, argon-helium mixture or argon-hydrogen mixture.
Argon is usually used for welding of minimum thicknesses, since this gas tends to lower the temperature of the weld pool; the arc subjected to helium protection, on the other hand, is much hotter and is used on materials with high thermal conductivity to increase the welding speed.
The price difference between the two gases significantly affects their choice; in fact argon costs less and is required in smaller quantities than helium, which being lighter than air requires application in greater quantities to ensure the right efficiency.
Blends, on the other hand, are used when protections with intermediate characteristics are required. Furthermore, the purity of the gas is of fundamental importance, since even minimal percentages of impurities can compromise the quality of the weld.
The infusible electrodes and filler rods
These can be pure tungsten or mixed with other elements, such as thorium, cerium or zirconium. Those in pure tungsten produce a very stable arc but must be used only in alternating current with low intensity, those in thorium withstand higher currents and are especially suitable for welding steel in direct current; the tungsten and zirconium electrodes, on the other hand, are used to weld aluminum while the cerium electrodes are used to make welds with high wear resistance.
Furthermore, in the case of welding thicknesses greater than 3 millimeters, the use of filler material is required to increase the strength and structure of the seam; also in this case, according to the type of material to be welded, specific filler rods are required.