When those who are interested in welding talk about fusion techniques, the subject of TIG welding is held in a certain reverence. Its reputation in this regard partly stems from its place in history as the method used for construction of a great many famous aircraft. Although developed initially in the 1920's, TIG (tungsten inert gas welding) wasn't used much because of W.W.II spurred further development as aircraft were being made lighter and lighter and TIG became the pre-eminent method of joining such non ferrous materials as aluminium and magnesium. The linde corporation  (now L-Tec) was the first company to capitalize on the technique, and after the war their trademark Heli-arc became the de-facto generic name for tig welding.

Besides the romantic beginnings, the TIG process has been considered quite special for other reasons. It does take considerable practice to be good at it, and because the equipment has always been rather expensive, a weldor who had one and was good with it developed a reputation particularly in the field of esoteric materials and exotic construction in aircraft and racecars. Basically an outgrowth of arc welding, the TIG process is done with a lightweight torch that uses a tungsten electrode to draw an intense, concentrated arc, shielded by an inert gas. The inert gas comes out of the torch, all around the electrode and displaces the air from the weld zone to exclude oxygen and nitrogen from contaminating the weld. Although helium was the original gas used, today argon is the most common shielding gas for TIG welding. The tungsten electrode is not considered a "consumable" item in the usual sense, since filler separate, hand held rods, much like in oxy acetylene welding, supply metal. In many ways, Heli arc welding is like a high tech version of the old-fashioned gas torch.

The concentrated nature of the TIG arc is one of its strong points. Welds of great strength and quality can be made on thin materials, light materials dissimilar materials in fact most available metals and all with minimal distortion or corruption of the adjoining base metal. The process does not generate sparks or spatter, and the welds are as clean as can be, which is why it is the method of choice in aircraft, race car construction, and stainless and aluminium products made for the medical, dental or food handling services. There’s is little slag involved, and because there is very little smoke generated, the weldor has a good view of the process, allowing to make very precise joints. The weldor has greater control with TIG than with most other welding methods. The amperage control is infinite because besides the settings on the power source, the weldor has a foot control he operates while he welds.

With TIG there are only a few disadvantages. There are very few jobs a TIG weldor can't do, but there are some jobs other techniques are better suited to for practical reasons. For big jobs, like welding up a car trailer or a big metal rack made from steel tubing, the TIG method is just to slow - an arc welder or MIG would be much faster, However, there are many applications in air craft and race car chassis work where a large project may be tediously done with a TIG, simply because a lightweight, high strength material like thin wall 4130 chrome-moly tubing is used where TIG would be the preferred method. For outdoors work, again an arc welder or flux core wire MIG are the best choices because they aren't as affected by air currents

The cost and complexity of the TIG system has kept it largely out of the hands of most small shops until in the last few years. Most large TIG set-ups are heavy and can weigh upwards of 200kgs and have to be moved with a crane or a fork lift truck and most professional units have a water-cooled torch assembly which often involves some plumbing connections in the shop besides the normal electrical hook ups. So the big shop-type TIG machines have always been about the most expensive welding machines available, which has increased their mystique but not widened their market. In the last few years, however, manufacturers have built smaller and lighter, solid-state-electronic TIG machines to make them more attractive to the small fabrication shop, race car shops and site workers. Many of these machines are now air cooled, and, at about one third of the cost of the traditional TIG machines, they are being seen out in the field more and more.

The basic components of the TIG set-up include the power supply, foot control, water circulation system and the torch. The latter differs from the other types of electric welding torches by being smaller and lighter and holding a central rod of tungsten as the electrode for the arc. Taking the torch apart there is a ceramic shield at the business end (called the ceramic or gas lens cup), then the collet, which retains the tungsten in the collet body, and the back cap. There is customisation of the torch, depending on the work to be done, in that there are different sized tungsten’s, different gas cups with shapes for specific kinds of jobs and different back cap lengths depending on how tight the quarters are where the weld has to be made. For instance, you could use a short tungsten and short back cap to fit into a tight corner better. The shape of the gas cup can create a different shape and size envelope of shielding gas over the weld area. From the larger welding machine companies, there’s a variety of different - size torch bodies with different amperage capacities as well as some special models made for tight confines.

Input voltage on TIG machines begins in the 220v range of single phase power, and the biggest professional boxes are for 460v three phase The professional units range in amperage capacity from 250amps to 650, though larger ones are the multi technique machines on which the high amperages are probably used only on the arc-welding process. It would be pretty rare to use more than 300amps on a TIG weld, unless you had to weld really thick aluminium plates or castings. When welding at 300 amps or more tiny bits of tungsten electrode can come off and become included in the weld, which would weaken the joint. The three-phase current models are definatly for shop use only, where the amount of shop equipment and power used every month makes the expense of transformers and rewiring the building economical over the long run in utility bills. Home shops generally do not have three-phase power.

On the small shop- scale of TIG machines (around 130amps) the functions are normally limited to scratch start TIG which is where there is no high frequency to start the arc there for the tungsten must be placed onto the welding piece before it can be struck. The smaller machines are normally limited to DC only to keep the costs down to a starter level and they are fine for welding steel up to around 5.00mm thick although this can vary positively and negatively depending on the quality of the machine.

In the medium range of TIG units (160-250amps) most of these require a larger input current than the small scale TIG machines and will require a 240v supply although again this can change with the brand and quality of the machine, some machines can even be powered by either 110v 240v or 415v although these machines tend to be around the £1800 mark with only the basic functions, whereas some machines with only 110V/240v with AC/DC capabilities of the same amperage are available for around £1200 and have many more features as standard.

The mid range machines also offer several special features, such as slope control. This refers to how the wave of current cycles when the machine is welding. Picture the wave as a curved line that goes up and down, crossed the base line and then curves back up and over again in repeated fashion many times a second. This is called a sinusoidal wave in alternating current. TIG machines use both AC and DC current, with the AC used for non-ferrous metals like aluminium or magnesium. One half of the AC wave is actually straight polarity and the other half is reverse polarity. The straight - polarity portion of the wave builds the heat in the arc, while the reverse current has the effect of cleaning the oxides from the aluminium being welded. So the TIG torch on AC is constantly cycling between a hot arc and a cleaning cycle, but at lower amperages the arc can be obstructed at the changeover point or actually go out. Most of the TIG machines have a special circuit inside that produces a high frequency, low power extra current that keeps the process going at all times. The high frequency control makes the TIG arc easy to start without touching the tungsten to the work, and makes a more stable arc while welding. On many machines the high frequency system can be set on the front panel of the welder to arc starting, off continuous use. On ferrous metal welding, the high frequency is used mainly for arc starting.

The slope control is a feature in which the weldor can adjust the parameters of the wave on the upside or the downside to get the perfect combination of penetration and cleaning action on aluminium. Even a clean piece of aluminium contains some aluminium oxides. In the base material and the slope adjustments allow a good weld to be made without these oxides being included in the bead. Some tig machines offer a Square-wave AC. The traditional sinusoidal wave with high frequency over it creates a lot of radio interference as well as some problems on welding aluminium. The square wave machines are all solid state electronics, with features that make a wave made of up and down squares instead of half circles this means the high frequency control intervenes a less often, and the same size electrode can be used at higher currents. This discussion of the current waves may be more than the home/shop user needs to know, but at least you may better understand the language used by manufacturers describe their equipment. Suffice it to say that the modern square wave technology and solid-state electronics are desirable features in a full-on TIG machine.

Another feature you may see mentioned is post flow. When you are making a bead and get to the end of your seam it's a good idea to allow gas to flow over the end of the weld as it cools, to keep out contaminants. On most professional machines, there is an adjustable timer that allows gas to flow for so many seconds after you have stopped the arc. You keep the torch in place just where you stopped and gas keeps flowing for a specified time. This is helpful on steel but essential on aluminium magnesium and brittle high strength steels like the 4130 used in aircraft and racecar construction. It's called post flow because it is post welding gas flow. The post flow of water and gas to the TIG torch also helps cool the tungsten electrode down to a point where it cannot be oxidised when regular shop air flows around it after the welding stops.

Some shop-type TIG machines feature water-cooled torches, but some are air cooled, with water-cooling systems as an option. Obviously the extra equipment for a water-cooling system as an option. Obviously, the extra equipment for a water-cooled torch adds to the total price of the package. In some shops, the water-cooling system consists of a unit added on to the basic power supply, containing 1-5 gallons of water, a water circulating pump and a small radiator and fan. It’s like a miniature automotive cooling system. In shops where amperage used can be quite high, or where long welds are made, the torch may be hooked to a source of regular cold tap water, and the heated return water flows back into the shops drain, this system uses more water but keeps the torch cooler than the recirculating systems.

The correct gas flow is very important in TIG welding although it is not much different from the process with MIG welding you will need a flow meter, which will regulate the flow of gas going through your torch. The flow meter can be set to allow different amounts of gas through, so for example if you were welding basic mild steel it would be recommended to have a gas flow between 8-10 cubic feet per hour. Argon is sufficient for welding up to 1/8" thick material, but the gas flow requirements go up with the amperage your machine is set at and the thickness and type of material you are welding, for stainless steel it would be recommended to use around 10-12 CFH whereas with Aluminium gas flow recommendation would go to around 15-20CFH for the same thickness as these are only our recommendations we do advise you test it for your self first as the variables are many.

Argon is certainly the basic, all-around shielding gas for the TIG process and is useable on virtually all metals. Straight helium is seldom used but often in production work a mixture of argon and helium is used to get the best properties of both gasses. Argon has the qualities of good arc starting, cleaning action and the best puddle control, while helium makes for a hotter weld for greater penetration and a faster welding speed, such as when welding thicker materials. An argon helium mix is often used to allow welding of non-ferrous metals at higher speeds. The helium in the mix helps make more heat for aluminium welding and some people have said it is like "adding a turbocharger"