Welding can be quite complex especially if you're just starting out but with the right welding process and proper use of it you can get the grip welding quite quickly. The same can be said for a process known as PAW. Plasma arc welding may seem similar to TIG welding since it does require a tungsten electrode, it uses something that TIG welding doesn't. This is plasma, which is forced through a fine-bore copper nozzle. This makes the plasma exit from the nozzle at temperatures of up to 28,000 °C. There is still an electrode in the torch's body so that the plasma arc is separated from the shielding gas envelope.
Advantages of Plasma Welding
Penetration
Unlike most welding processes, plasma welding is able to provide greater penetration. For reference, TIG welding allows you to make seams as thick as 3 mm. With a plasma welding setup, you can make T-seams that are up to 10 mm thick.
Power
The power of plasma arc welding machines allows you to weld through thinner materials much easier. This is thanks to the more stable arc and the power of current the welder is able to handle.
Sensitivity
With a plasma welder, you also get lower sensitivity. While this seems like a bad thing at first, it can be used to your advantage. This means you can weld long pieces without much variation in the size of the plasma column.
Lifespan
Since the tungsten of a plasma welder is built into the torch, there are fewer chances for tungsten inclusions. This in itself makes the electrode last longer and thus the welder.
Automation
A great feature of plasma welders has to do with the future. Automation may not be as important nowadays but it will be soon and as you know plasma welders are easy to robotise.
Types of Plasma Welding
Microplasma
The current in microplasma welding is between 0.02 and 15 amperes making it ideal for the thinnest pieces of metal.
Keyhole
Using the keyhole plasma arc welding process your current levels may vary from 15 to 350 amps which will largely depend on the thickness of the material you're welding.
Melt-in
With the melt-in welding technique, you get to use anywhere between 12 and 100 amps which makes it a similar process to TIG.
Transferred
Using the transferred PAW method you have direct polarity DC current on your side. This current has the tungsten electrode allied to the -VE terminal while the metal is allied to the +VE terminal and thus produces a solid joint between sheets of metal. This is thanks to the heating capacity of the method which enhances the properties of the two metal pieces.
Non-Transferred
With a non-transferred PAW method, you essentially have the tungsten electrode to the -VE terminal again but the nozzle is connected to the +VE pole. This is where the arc is generated between the nozzle and electrode and thus enhances the ionisation of the gas in the torch. The ionised gas is then used to join thin sheets of metal.
Plasma Welding Equipment
Torch
The most notable and most important piece of plasma welding equipment is the torch. A plasma welder torch, as you already know, looks a lot like the one used in TIG welding. But the difference here is that PAW torches are water-cooled as the arc is inside the torch even when it's being used. This creates high temperatures and because of that, a water jacket is needed to cool down the torch.
Filler
What acts as the glue between the two metal pieces you're joining is the filler material. Although usually when it comes to PAW there is no filler material used, in cases where it is, this material it's fed directly into the weld zone.
Shielding and Plasma Supply
There are two gases a plasma arc welding process uses, a shielding and a plasma gas. You need to have a supply of both with the former making sure that the low pressure needed to perform the weld doesn't cause any turbulence. The latter is an ionised hot gas which is essentially the main energy source for PAW. Shielding gas makes the high flow rate possible while plasma gas is what makes everything happen in the first place.
Recirculator
A water recirculator is used to form the water jacket mentioned above. This piece of plasma welding equipment is what keeps water flowing and the torch cool. Without it, the torch would easily end up damaged. So make sure to take care of the recirculator if you want your torch to be in good shape.
Power Supply
As with any type of welder, a PAW welder also needs a power supply. This needs to be a high-power DC supply that allows the welder to generate the electric spark needed between the tungsten electrode and the welding plates. With this type of power supply, you can weld at a minimum of 2 amps and at a maximum of 300 amps but you'll need 80 volts in order to be able to do this. The power source of a PAW welder is made up of a rectifier, transformer, and control console.
