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Understanding plasma arc welding (PAW)

Today I will be discussing the definition, applications, diagram, equipment, working, advantages, and disadvantages of plasma arc welding (PAW). Previously, some articles was published on arc welding process. Check out!

What is plasma arc welding (PAW)?

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 create shields to the arc plasma. Same as TIG welding, filler metal may be or may not be added.

Read more: Understanding gas welding process

Watch the video below to learn the working of plasma arc welding (PAW):

Read more: Understanding flux-cored arc welding (FCAW)

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, special torch, using nozzle to separately pushed the arc and shielding gas to the torch. The arc is constricted 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 form by two gas flow: 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 blow 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.

Read more: Different types of electric arc welding

Components and equipment

The followings are the components of plasma arc welding.

  • Current and gas decay control: it is used to properly closed the keyhole while terminating the weld in the structure
  • Fixture: it helps to avoid the atmospheric contamination of the molten metal under 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 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

Read more: Working principles of arc welding

Plasma arc welding machine:

automated plasma arc welding machine

diagram of plasma arc welding PAW

Read more: Understanding submerged arc welding

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 and disadvantages of Plasma arc welding (PAW)

Advantages

The followings are the benefits of plasma arc welding:

  • 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 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

Read more: Safety precautions in a gas welding workshop

Disadvantages

Despite the good advantages plasma arc welding offers, it still has some limitations. The followings are disadvantages of the welding process.

  • 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 the definition, applications, diagram, components and equipment, working, advantages, disadvantages of plasma arc welding PAW are being discussed. I hope you enjoyed the reading, if so, kindly share with other students. Thanks for reading, see you next time!

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