Tungsten Inert Gas Welding(TIG): Definition & Working

Tungsten inert gas (TIG) welding is a type of arc welding that uses tungsten as an electrode and the electrode is non-consumable in nature. This welding is also known as Gas tungsten arc welding (GTAW).

Today in this paper we will see the Definition, Main parts or Equipment, Working principles, Advantages, Disadvantages, and Applications of Tungsten Inert Gas Welding.

What is TIG Welding|GTAW?

Tungsten inert gas (TIG) welding is one type of arc welding method where we use a non-consumable tungsten electrode, to weld the two metallic bodies. The weld spot is protected from contamination by helium, argon, and other inert shielding gases.

Tungsten Inert Gas (TIG) welding, also known as Gas Tungsten Arc Welding (GTAW) is an arc welding process that produces the weld with a non-consumable tungsten electrode.

Tungsten Inert Gas Welding

Tungsten inert gas (TIG) welding became an overnight success in the 1940s for joining magnesium and aluminum. Using an inert gas shield instead of a slag to protect the weld pool, the process was a highly attractive replacement for gas and manual metal arc welding.

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TIG has played a major role in the acceptance of aluminum for high-quality welding and structural applications.

Shielding gas use in Gas Tungsten Arc Welding

Shielding gas is selected according to the material being welded. The following guidelines may help:

  • Argon: the most commonly used shielding gas which can be used for welding a wide range of materials including steels, stainless steel, aluminum, and titanium.
  • Argon + 2 to 5% H2: the addition of hydrogen to argon will make the gas slightly reducing, assisting the production of cleaner-looking welds without surface oxidation. As the arc is hotter and more constricted, it permits higher welding speeds. Disadvantages include the risk of hydrogen cracking in carbon steels and weld metal porosity in aluminum alloys.
  • Helium and helium/argon mixtures: adding helium to argon will raise the temperature of the arc. This promotes higher welding speeds and deeper weld penetration. The disadvantages of using helium or a helium/argon mixture is the high cost of gas and difficulty in starting the arc.

Construction Or Parts

A Tungsten Inert Gas Welding Machine consists of the following equipment:

  • Power Supply
  • Inert Gas Supply
  • Welding Torch/Holder
  • Tungsten Electrode
  • Shielding Gas
  • Filler Rod
Construction of Tungsten Inert Gas Welding

1. Power Supply:

In TIG welding we need a constant power supply because if there was a fluctuation of current then it is hard for the welder to weld the joints properly.

The power supply can be two types:

  1. DC Power Supply
  2. AC Power Supply

In the DC power supply, we can weld steels, nickel, titanium, etc. And in AC power supply, we can weld magnesium, aluminum, etc. materials.

2. Inert Gas Supply:

In TIG Welding, we need an inert gas supply to provide the shielding to the weld area from the atmospheric gas (For example, Oxygen, Nitrogen, and Hydrogen).

In general, Argon is used as an Inert gas supply in TIG Welding. We will discuss this later on the Shielding gas section.

3. Welding Torch:

In TIG Welding the welding torch is designed to do either automatic and manual operations. However, in terms of construction, both are the same, in the manual torch, they are provided with a handle to hold, and in the case of automatic, they are designed to mount on an automatic machine.

Torches are provided with a cooling system either by water or air.

When the Ampere of the current is less than 200 A generally, we use air-cooling, but if it exceeds 200 A then we use water cooling to decrease the temperature of the welding torch.

The inside portion of the welding torch is generally made of copper to increase the conductivity of heat.

And the torches are provided with a holding arrangement (Port) to hold the Tungsten electrode firmly.

4. Tungsten Electrode:

In TIG Welding we use a non-consumable electrode made of Tungsten or Tungsten Alloy.

Due to the High-temperature resisting capacity (the Melting Temp of Tungsten is 3,422 °C) of tungsten rather than any other metal, that’s why we use the tungsten electrode.

The diameter of the electrode is generally varying from 0.5 mm to 0.65 mm, and the length varies between 75 mm to 610 mm.

5. Shielding Gas:

Shielding gases are used to protect the welding pool from atmospheric gases like nitrogen, oxygen otherwise these gases can damage the welding surface by creating porosity, blowhole, etc.

Choosing Shielding gases depends on the types of welding as well as the atmospheric condition along with the type of metal used for the operation and many more.

However, generally, we use Argon as a shielding gas in TIG Welding. Sometimes Argon-helium mixtures are also used in this type of welding.

6. Filler Rod:

As we already know, in TIG Welding, we use a non-consumable electrode that is Tungsten, so in some cases, we need separate material to fill up the gap between two joints.

The material of the filler rod can be anything, like carbon steel, aluminum, etc. It generally depends on the type of joints, the work-piece material, thickness, and also the properties of the workpiece.

Working Principle

When we switch on the machine the high-frequency generator provides an electric spark.

The electric spark is struck between the Workpiece and the Electrode either by touching the electrode by scrap material or by using a high-frequency unit.

We need to do this operation (Touching with the scrap material) at least 2-3 times to warm up the electrode before the actual operation started. Due to this, we can save the breaking of the electrode tip.

In actual operation, the heat generated by the electric spark fuses the metal from the joint area and it produces a molten weld pool. The size of the pool depends on the size of the electrode and the amount of current supplied by the generator.

The arc area is surrounded by an inert or reducing gas shield to protect the weld pool and the non-consumable electrode.

The process may be operated autogenously, which means without filler material or filler material may be added by feeding a consumable wire or rod into the established weld pool.

Tungsten Inert Gas Welding produces very high-quality welds across a wide range of materials with thicknesses up to about 8 or 10mm.

Applications of TIG/GTAW Welding:

  • This is specially used in the welding of the refractory, sheet, and reactive materials.
  • Tungsten Gas welding can be used with such a large variety of metals, the process can be applied to several industries and aid in the creation and repair of many items. This form of welding is common in the aerospace, automotive, repair, and art fields.
  • Aerospace: Aircraft and spacecraft are constructed in part by means of TIG welding.
  • Automotive: Safe and secure construction is essential in the auto industry, as is making vehicles stand the test of time.
  • Repair: TIG may be used in a number of repair applications. From fixing a child’s toy, like a wagon or old-fashioned pedal car, to repairing aluminum tools, this welding method comes in handy.

Advantages of TIG/GTAW Welding:

The advantages of Tungsten Inert Gas Welding are the following:

  • Tungsten welding offers a solution for welding critical joints, and for situations where small or exceptionally precise welds are required.
  • It can be performed with a wide variety of metals
  • And, when done correctly, it produces a high-quality and high-purity weld compared with other joining processes, which is crucial in many applications.
  • It can be done in both automatic and manual.
  • Overall, it is one of the most efficient ways to join two metals.
  • No slag is produced.
  • TIG Welding can be done in any position.

Disadvantages of TIG/GTAW Welding:

The disadvantages of TIG Welding are mentioned below:

  • Tungsten welding cannot be used for thicker sheets of metals.
  • More complicated-High Skilled and professional workers are needed.
  • The safety issue, welders are exposed to the high intensity of lights which can cause eye damage.
  • The price of TIG welding services is high. However, costs will vary depending upon the materials being welded, and the scope of the project.
  • It is a slow process of welding.