Information of Plasma Welding

Plasma welding machines melt areas with an arc and then use a high-velocity, high-temperature ionized gas to make welds. The process of plasma welding is used to bring better control to the arc welding process in lower current ranges. It provides an advanced level of control and accuracy in order to produce high quality welds in miniature or precision applications and to provide long electrode life for high production requirements.

Plasma is gas, such as argon, which is heated to an extremely high temperature and ionized so that it becomes electrically conductive. It is commonly known as fourth state matter (after solid, liquid, and gas) and consists of free electrons, positive ions, atoms, and molecules. The high-velocity ionized gas conducts electricity from the torch of the plasma welder, heats the workpiece, and then melts the material. Plasma welding is similar to Tungsten gas (TIG) welding. In both processes the arc is formed between the end of a small diameter tungsten electrode and the workpieces, but in plasma welding the electrode is positioned behind a fine bore copper nozzle in the torch. Plasma is formed by forcing the arc through the nozzle and creates a characteristic columnar jet.

The arc’s contact with the working surface creates a high-heat circuit which can melt a section less than 1/16 in. (1.6mm) wide. With some plasma welding machines, the plasma arc travels through the nozzle at a speed of up to 20,000 feet per second, and at temperatures as high as 30,000º F.

The many benefits of using plasma welding include the precision, ability to weld small parts, and high production capabilities. Plasma is a very precise welding process due to the stable, concentrated arc, and forgiveness in the arc length variation (+/- 15%). The ability to weld small parts is important for delicate welding applications such as medical equipment. Small part welding is possible due to the low average capabilities (as low as .1 amps), it is stable at low amps, and it has a gentle arc transfer with no frequency noise. Plasma welding has short weld times and longer electrode life which contributes to its ability to do high production welding. A high performing plasma machine can produce exceptionally high quality welds.

Applications

Plasma welding machines are used in many applications. They provide high-quality welds and fast travel speeds. Some plasma welding machines are used in metal working, switch gear construction, and part fabrication applications. Others are used in the manufacture of heating, ventilation and air conditioning (HVAC) systems. Plasma welding can be used for high volume welding of strip metal, to precision welding of surgical instruments, and automatic repair of jet engine blades.

Plasma welding machines should adhere to American National Standards Institute (ANSI) standards.

Source: IEEE GlobalSpec