Plasma cutting is a process that is used to cut steel and other metals of different thicknesses (or sometimes other materials) using a plasma torch. In this process, a gas (oxygen, air, inert and others dependant on material) is blown at high speed out of a nozzle; at the same time an electrical arc is formed through that gas from the nozzle to the surface being cut, turning some of that gas to plasma. The plasma is hot enough to melt the metal being cut and moves fast enough to blow molten metal away from the cut.
A plasma torch requires you to start an arc between the electrode in the torch and the work you intend to cut. To start this arc there are various methods used, commonly High Frequency or Blow Back. HF (High Frequency) is used in most modern industrial plasma systems and in many older systems. The second common method is known as blow back, or short circuit start.
In both methods you achieve a pilot arc, which is an ionized path of gas between the electrode and nozzle in the torch. Once this pilot arc is brought close to the work, which is at the same potential as the nozzle, current will transfer directly from the electrode to the work. The plasma source will detect the current into the work and disconnect the nozzle (in most cases) allowing full current flow from the electrode to nozzle.
Plasma is an effective means of cutting thin and thick materials alike. Since plasma cutters produce a very hot and very localized “cone” to cut with, they are extremely useful for cutting sheet metal in curved or angled shapes.