Plasma welding

In plasma welding, plasma torches are used to obtain plasma, consisting of a tungsten electrode, water cooling pipes, gas supply, and a plasma nozzle.

The temperature in the plasma arc reaches 30,000 ° С, in contrast to the plasma of the electric arc, the temperature of which is 5000–7000 ° С.

In the plasma torch, the gas forming the plasma is introduced into the zone of the plasma arc. The gas is heated by an arc and ionized. Due to the thermal expansion of the gas, increasing the gas volume by 50–100 times, its high-speed outflow from the nozzle channel of the plasma torch occurs. The kinetic energy of ionized gas particles and thermal energy are the main sources of energy for welding.

The plasmatron mainly uses direct current burners.

The following varieties are possible in plasma welding:

• welding by a plasma arc burning between a non-consumable electrode and a workpiece,
• welding with a plasma jet burning between a non-consumable electrode and a plasma torch nozzle. Plasma is blown out by a gas stream.

As a plasma-forming gas are used: nitrogen, oxygen, argon, air.

Depending on the current in the plasma, the following types of plasma welding are distinguished: microplasma (0.1–250 A); at medium currents (50-150A); at high currents (current more than 150A).

Microplasma welding avoids burns in the metal. Welding at high currents occurs with the complete penetration of the metal. It is possible to weld thicknesses up to 8 mm in one pass, without cutting edges, which saves production time spent on preparing the edges and time spent on several passes.

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Plasma arc welding, unlike electric arc welding, has the following advantages:

• in plasma welding, the welding process is less sensitive to changes in the length of the electric arc;
• the process proceeds with a higher temperature;
• has a smaller diameter of the arc, which has a cylindrical shape;
• the arc burns at low currents - from 0.2 to 30 A.

It is divided into professional and unprofessional.

Unprofessional are domestic PLAZAR devices (universal, mobile plasma apparatus), Multiplaz, Gorynych. Designed for welding small volumes of metal and thickness, used for manual welding. Typically, a plasma jet is obtained using alcohol solutions or water.

To professional ones, designed for permanent use in production, working in an argon shielding gas environment, for welding large volumes of metal, for automatic welding - SBI (Austria), Migatronic (Denmark), EWM (Germany) and others.

Such devices as FoxWeld PLASMA 33 Multi, BLUE WELD BEST PLASMA 60 HF, Helvi Combi PC 302 and others do not belong to plasma welding machines, they belong to plasma cutting machines.

Nikolaev G. A. Welding in mechanical engineering: a Handbook in 4 volumes. - M.: Mechanical Engineering, 1978 (1-4 tons).

Articles:

1) Distinctive features of plasma welding

http://awg-tech.ru/plazmennaya-svarka

2) Plasma spot welding: features, advantages and applications

http://www.awg-tech.ru/plazmennaya-tochechnaya-svarka-osobennosti-preimushhestva-i-prim

3) Plasma seam welding: features and advantages when welding various metals

http://www.awg-tech.ru/plazmennaya-shovnaya-svarka-osobennosti-i-preimushhestva-pri-sva

Other links:

http://www.osvarke.com/plasma.html

http://rezhemmetall.ru/plazmennaya-svarka-metalla.html