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Plasma Arc Welding: Definition, Construction, Working Principle, Applications, Advantages, ands Disadvantages [With PDF]

Plasma Arc Welding is a liquid state welding process. Here in this paper, you are going to learn the Definition of Plasma Arc Welding, Components and Working Principle of the Machine, along with the Applications, Advantages, and Disadvantages of this Welding. So now let's get started with the definition of PAW!

What is Plasma Arc Welding?

Plasma Arc Welding (PAW) is a liquid state welding process in which the metal to metal joint forms in a molten state with the help of hot ionized gases known as Plasma. These hot ionized gases used to heat the work plates, and the joint is created due to fusion. 

Artificial plasma
Artificial Air Plasma

Construction of the Machine:

The Plasma Arc Welding setup consists of the following components:

  • Power Supply
  • Plasma Welding Torch
  • Water re-circulator
  • Tungsten Electrode
  • Shielding Gas
  • Plasma Gas 
  • Torch Accessory Kit (Tips, ceramics, collets, electrodes set-up gages)
  • Filler Material
components of plasma arc welding machine
A Line Diagram of Plasma Arc Welding Machine, Learn Mechanical

Let me give you the brief overview of each components.

Power Supply:

The plasma arc welding process needed a high power DC supply to generate the electric spark in between the tungsten electrode and welding plates.

This welding can weld at a low 2 amp and the maximum current which it can handle is about 300 amp. It needs about 80 volts for proper working.

The power source consists of a transformer, rectifier and control console.

Plasma Welding Torch:

This is the most important part of the plasma welding process.

This torch is quite similar as used in TIG welding.

PAW torches are water-cooled because the arc is contained inside the torch which produces high heat, so a water jacket is provided outside the torch.

DC plasma torch
DC Plasma Torch

Water Re-circulator:

This mechanism is used to cool the welding torch by the continuous flow of water outside of the welding torch.

Tungsten Electrode:

In this machine, we use a no-consumable tungsten electrode. As we know tungsten can withstand very high temperature.

Shielding Gas:

In this welding process, we use two inert gases. We need to maintain a low pressure to avoid the turbulence while welding due to this low-pressure gases welding shield is formed weekly, that's why we need to charge another inert gas through the outer portion of the welding force in high flow rate, to make the weld shield sustainable.

The inert gases which are used in this process can helium, argon, and also hydrogen as per the need, and it is totally depends on the temperature.

Plasma Gas:

It is an ionized hot gas composed of nearly the same numbers of electrons and ions. It has sufficient energy to free electrons from molecules, atoms, and electron to synchronise.

It is the main energy source of this welding.

Torch Accessory Kit:

These kits are used to expanding the performance of the welding torch.

Filler Material:

In Plasma welding there is no filler material is used. If the filler material is used, then it is directly fed into the weld zone.

Working Principle of Plasma Arc Welding Machining:

This is an arc welding process, a concentrated plasma arc is produced with the help of high-frequency unit of the machine and directed towards the weld area.

The plasma starts between the tungsten electrode and the orifice by a low current pilot arc. The plasma arc welding is concentrated because it is forced through a relatively small orifice or nozzle to increase its pressure, temperature and heat.

Because of the above characteristic, the arc will now become very stable, improved in shape and heat transfer rate.

The temperature of the arc is as high as 33,000°C due to this phenomenon heat the nozzle is surrounded by a water cooling system to avoid wear out of the nozzle due to heat.

Operating currents usually are less than 100 amp. This makes Plasma Welding different from other types of welding.

When filler metal is used it is fed into the arc as is done in Gas Tungsten-arc Welding. Arc and weld-zone shielding are supplied by means of an outer shielding ring and the use of inert gases like argon, helium or mixtures.

You may watch this video for a better understanding of the Plasma Arc Welding Process:

Advantages of PAW:

The advantages of Plasma Arc Welding are following:

  • Torch design allows better control of the arc.
  • This method provides more freedom to observe and control the weld.
  • The higher the heat concentration and plasma jet allow faster travel speeds.
  • The high temperature and high heat concentration of plasma allow the keyhole effect.
  • This provides complete penetration with the single-pass welding of many joints.
  • The heat-affected zone is smaller compared to GTAW (Gas tungsten arc welding).
  • It uses less current input as compared to another welding process.

Disadvantages of PAW:

The disadvantages of Plasma Arc welding are:

  • It produces wider welds and heat-affected zones compare to LBW and EBW.
  • Plasma welding equipment is very costly. Hence it will have a higher startup cost.
  • It requires training and specialization to perform plasma welding.
  • It produces ultraviolet and infrared radiation.
  • The method produces higher noise on the order of about 100dB.
  • The torch is bulky and hence manual welding is a bit difficult and requires training as mentioned.

Applications of PAW:

The application of Plasma Arc welding are:

  • This welding is used in marine and aerospace industries.
  • This is used to weld pipes and tubes of stainless steel or titanium.
  • It is mostly used in electronic industries.
  • Also, this is used to repair tools, die, and mould.
  • This is used for welding or coating on a turbine blade.

So this is all about Plasma Arc Welding Machining, I hope you enjoyed this article. I also wrote articles on some other welding processes do check out those too. And moreover do not forget to share the article on your favourite social platform.

More Resources:

Media Credits:

  • Image 1: By Chocolateoak – Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=12260232
  • Image 2: By Rudolfensis at English Wikipedia, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=45785285
  • Image 3: By Saubhik Roy- Design Team Learn Mechanical
  • Feature Image: By Saubhik Roy- Modified by Author
  • Video: By Chip CM


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