TIG
TIG or GTAW Welding Overview
Tungsten Inert Gas (TIG) or Gas Tungsten Arc Welding (GTAW)
Gas tungsten arc welding (GTAW) is also known as tungsten inert gas (TIG) welding. This is essentially an arc welding process.
In TIG nonconsumable tungsten electrode passes a constant current from welding power supply. This current is conducted across the arc through the column of highly ionised gas to produce the weld.
Gas Tungsten Arc Welding may use consumable filler rod as the weld deposit. However, in some GTAW welding processes (autogenous welds) filler wire is not required.
Same as with MIG, TIG uses shielding gas (usually inert gas like argon) to prevent contamination of the weld pool. But other non-inert gasses can be used, thus TIG is generally known as Gas Tungsten Arc Welding (GTAW).
Tungsten Inert Gas (TIG) or Gas Tungsten Arc Welding (GTAW) Process
In TIG / GTAW the welding arc is produced by welding current passed through the tungsten electrode.
The separation between the electrode and the workpiece is approximately 1.5mm-3mm for the arc to occur.
Once the arc is struck, the welder moves the welding torch in small circular motion. Then, the torch is tilted 10-15 degrees.
If filler metal is used then it is added to the front end of the weld pool. At all time the constant separation between the electrode and the workpiece is maintained. The filler rods have low melting points. Therefore, it is essential that filler metal is not too close to the arc.
As with MIG, TIG / GTAW uses shielded gas to prevent contamination. If filler rod is used it must stay inside the gas.
Gas Tungsten Gas Welding (GTAW) welder consists of:
- Welding Power Supply to deliver electrical energy
- Welding Torch contains tungsten electrode, shielded gas passage and electrical conductor
- Cooling system to prevent overheating
- Shielded gas supply
- Workpiece
Tungsten Inert Gas (TIG) / Gas Tungsten Arc Welding (GTAW) 3 operational modes:
- Direct positive current (weld expose to large heat)
- Direct negative current (electrode exposed to large heat but oxide layers removed)
- Alternating (combination of positive and negative)
Tungsten Inert Gas / Gas Tungsten Arc Welding Welder's Components
The typical TIG / GTAW welder station has five distinct components:
- Welding Power Supply to deliver electrical energy
- Welding Torch contains tungsten electrode, shielded gas passage and electrical conductor
- Cooling system to prevent overheating
- Shielded gas supply
- Workpiece
TIG / GTAW Welder's Components: Power Supply
Gas Tungsten Arc Welding uses constant current source. This ensures that heat is relatively constant.
The polarity of the TIG / GTAW power supply depends on application. Two modes are employed: positively and negatively charged electrode.
Negatively charged electrode welders use to weld steels, nickel, titanium and other metals. Positively charged electrode is used for shallow welds (less heat is produced at the workpiece).
There is also another mode - alternating current. This mode switches between positive and negative polarity.
Alternating current mode is used to weld aluminum and magnesium. It prevents electrode overheating while maintaining heat at the workpiece.
TIG / GTAW Welder's Components: Welding Torch
TIG / GTAW welding torch can be automatic or manual. Manual torch has a handle and the automatic one has a mounting rack. Inside the torch there is nonconsumable tungsten electrode, outlets for the shielding gas and conductive alloys. Conductive alloy - collet - holds tungsten electrode. The body of the welding torch is made of insulating plastics. The plastic insulates against electrical conductors and the heat.
TIG / GTAW Welder's Components: Cooling System
Tungsten Inert Gas / Gas Tungsten Arc Welding uses cooling module. It is connected to the welding torch by in and out cooling hose. TIG / GTAW uses water or air as the coolant. Both are supplied by the cooling system
Tungsten Inert Gas / Gas Tungsten Arc Welding: Shielding Gas Supply
TIG / GTAW uses shielding gas to prevent contamination of the welding pool. Oxygen and Nitrogen can easily cause porosity or fusion during welding process. Inert gases such as argon or helium are mainly used as the shielding gas. The choice of gas depends on application. Argon is most common, especially with alternating current. Helium on the other hand allows deeper weld penetration. Mixtures are common (where 75% or higher is made up of helium). Sometimes hydrogen is added.
TIG / GTAW Welder's Components: Workpiece or Welded Material
The workpiece is a material on which weld is being deposited. It is also connected to power supply to complete the circuit during welding. For Gas Tungsten Arc Welding workpiece is connected to the electrical ground.
TIG / GTAW Welder Component Summary
- TIG / GTAW Cooling System
- TIG / GTAW Power Supply
- Shielding Gas Supply
- TIG / GTAW Welding Torch/Gun
- Shielding gas released during welding
- Filler Rod
- Workpiece
TIG / GTAW Welder
