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What is plasma arc welding (PAW)?
This is another type of arc welding process that uses a non-consumable electrode just like tungsten inert gas welding (TIG), making them a similar process. It creates an arc between the electrode and the workpiece.
Plasma arc welding (PAW) coalescence is produced by heat obtained from a constricted arc setup between a tungsten electrode and the constricting nozzle, which is a non-transferred arc. It can also be between a tungsten/alloy tungsten electrode and the workpiece, which is a transferred arc.
This process has the ability to use two inert gases, one forms the arc plasma and the other creates shields to the arc plasma. Same as TIG welding, filler metal may or may not be added.
PAW welding is said to be an advance of TIG welding. in TIG welding, the open arc is shielded by argon and helium, but in plasma, a special torch uses a nozzle to separately pushed the arc and shield gas to the torch.
The arc is constricted and pushed by a water-cooled small-diameter nozzle by squeezing the arc, increasing its temperature, pressure, and intense heat, helping to improve the arc stability.
Just as mentioned earlier, PAW arcs are formed by two gas flows: luminal and turbulent flow. The luminal flows at low pressure and low flow of plasma gas, which is employed to ensure that the molten metal is not blown out of the weld zone. Whilst, the turbulent flows at high pressure and high plasma gas flows. These gases are argon, helium, hydrogen, or could be their mixture.
Watch the video below to learn the working of plasma arc welding (PAW):
Diagram of Plasma Arc Welding
Components of Plasma Arc Welding
The followings are the components of plasma arc welding.
- Current and gas decay control: it is used to properly close the keyhole while terminating the weld in the structure
- Fixture: it helps to avoid the atmospheric contamination of the molten metal under the bend
- High-frequency generator and current limited resistors: this is used for arc ignition. Its starting system of the arc may be separate or built into the system
- Plasma torch
- Power supply: it uses a direct current power source either a generator or rectifier
- Shielding gases: the two inert gases or mixtures of gases used
- Voltage current: this is required in contour welding
Plasma Arc Welding Machine
Applications
Micro-plasma welding is traditionally used for welding thin sheets at a minimum of 0.1mm thickness and wire and mesh sections. It is used in the marine and aerospace industries. Plasma arc welding is used to weld pipes and tubes of stainless steel and titanium.
It is a good choice when repairing tools and dies. This welding process is also used for welding and coating on a turbine blade. Finally, plasma arc welding is widely used in electronic industries.
Advantages of Plasma arc welding (PAW)
Below are the benefits of PAW
- Ability to cut all metals
- It allows better control of the arc
- Due to the higher heat production and the plasma jet allows faster travel speeds
- Heat affected zone is similar to GTAW
- High heat concentration of plasma allows a keyhole effect, which provides complete penetration with a single pass welding of many joints
- It provides more freedom to absence and controls the weld
- It can cut metals even faster than oxy-fuel welding
- PAW welding is easy to automate
- It leaves narrower kerf
Disadvantages of Plasma arc welding (PAW)
Below are the limitations of PAW:
- Plasma welding equipment is expensive
- It requires specialized training and personnel to perform the operation
- Higher noise is produced.
That is all for this article, where I explained what plasma arc welding is, its applications parts, equipment, advantages, and disadvantages. I hope it was helpful, if so, kindly share with others. Thanks for reading, see you around!
