Overview of Plasma Welding

Since its creation in 1957, plasma arc welding has become one of the most reliable forms of welding in today’s world.  Plasma welding is a process where the electrode is inserted into a small nozzle which allows the gases being used to be separated.

Plasma welding is similar to gas tungsten arc welding, where the electric arc is made using an electrode and the piece you are welding.  In plasma welding the plasma is forced through a fine-bore copper nozzle that makes the plasma come out at a far greater velocity and a much higher temperature than when you use gas tungsten arc welding.

Some of the main benefits of using the plasma arc welding method are the ability to make precision welds on thinner types of material with more accurate precision, thereby allowing welders the ability to make better use of their skills.

With the ability to stream their arc into harder to weld areas, this type of welding offers many new opportunities for welders.  With the availability of plasma welding machines and processes that can be run either manually, which allows the welder more room to observe and control the weld,  or automatically, the production of very straight and thin welds is now possible.

Plasma arc welding can be used on all metals that are weldable with the gas tungsten method.  There are many variations to take into account when you are using the plasma arc welding method such as the varying current, plasma gas flow rate and the diameter of the orifice you are using, including:

  • Micro-plasma (< 15 Amperes)
  • Melt-in mode (15-400 Amperes)
  • Keyhole mode (>100 Amperes)
  • Plasma arc welding has a greater energy concentration as compared to GTAW
  • A deep, narrow penetration is achievable, with a maximum depth of 12 to 18 mm (0.47 to 0.71 in) depending on the material
  • Greater arc stability allows a much longer arc length (stand-off), and much greater tolerance to arc length changes
  • PAW requires relatively expensive and complex equipment as compared to GTAW; proper torch maintenance is critical
  • Welding procedures tend to be more complex and less tolerant to variations in fit-up, etc.
  • Operator skill required is slightly greater than for GTAW
  • Orifice replacement is necessary

Plasma arc welding is becoming the industries norm as it allows for more consistent welds, and requires less force being applied to the pieces you are welding and tends to reduce damage caused by heat to adjacent parts.  With smaller burn areas than gas tungsten, plasma welds tend to have more parallel sides, which cause less angular distortion.

The higher heat offered by the plasma technique provides the ability to produce more stable welds, which provide the welder with more variation in joint alignment, proving useful in pipe work and wherever a one-side weld is required.  With the advancement of plasma welding techniques, it is possible to weld metal as thin as foil using a low current.

Plasma welding can be a more dangerous method of welding because of the high velocity involved and the high temperatures.  When plasma welding, welders typically use at least two separate flows of gas which adds to the danger involved in this process.  When using the plasma method welders must be sure to take into account the gas flow rate, which must be carefully controlled and monitored based on the current, gas mixture, and the type of metal you are working with and the diameter of the orifice being used.

Always remember safety is the most important thing to be aware of when welding.  Utilizing the proper safety precautions and protective gear can make all the difference.

With the ability to join practically all metals available, it’s no wonder that plasma arc welding is the more productive and favorite among welders.  With its ease of use and precision, plasma arc welding looks to be the favorite for a long time to come.