Plasma Arc Welding | Transferred Type Plasma Arc Welding | Non-transferred Type Plasma Arc Welding

Plasma arc welding

Plasma arc arc welding (PAW) is some types of arc welding in which an arc is created between a pointed tungsten electrode and the work piece to be joined together. The plasma arc, on the other hand, may be isolated from the shielding gas envelope by situating the electrode inside the torch’s body.

Plasma arc welding is a procedure that was first established in 1953 and is now considered the industry standard in a number of sectors. This method of welding produces are quicker, more dependable, and produce less heat.  The fact that it produces less heat means that it is more adaptable and may be utilised in a wider range of applications than the other types of arc method.

Plasma welding may be used to create both key hole and non-key hole welds, depending on the application. A non-keyhole weld may be produced on work pieces with a thickness of 2.4 mm or less using this procedure.

A non-keyhole weld may be produced on work pieces with a thickness of 2.4 mm or less using this procedure.

Types of Plasma Gas

On mild steel, stainless steel, and aluminium, air is the most versatile plasma gas is used because it delivers excellent cut quality as well as rapid cutting speed. Due to the fact that air is abundant, it cuts the operating costs as well.

When plasma engraving, argon gas is used. When cutting thicker stainless steel or aluminium, it is common practice to employ a combination of Argon and Hydrogen.

Principle of Plasma arc welding

Plasma is nothing but a high temperature ionized gas. It is generally a mixture of positively charged atoms and neutral charged atoms and free elements. When this high temperature plasma is passed through the orifice, the proportion of the ionized gas is increased and the plasma arc welding is formed.

Working of Plasma arc welding

When the high heat content plasma gas is forced through the torch orifice surrounding by negative tungsten electrode in the form of jet. The plasma cutting force imposes a swirl on the orifice gas flow. The arc is initiated in the beginning by supplying electrical energy between nozzle and tungsten electrode. This will release high energy and heat. This heat is normally in between 10,000C t 30,000C.

Types of Plasma arc welding

This high amount of heat energy is used to weld the metal. There are two types plasma Arc welding used practically..

1. Transferred type Plasma arc welding

In transferred type, the tungsten electrode is connected to the negative terminal, work piece is connected to the positive terminal. An electric arc is maintained between the electrode and the work piece heats a co-axial flowing gas and maintain it in a plasma state. It is difficult to initiate the arc first between the work piece and the electrode. For that, the pilot arc is struck between the nozzle and the electrode.

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2. Non-transferred type Plasma arc welding

In this type, power is directly connected with the electrode and the torch of nozzle. The electrode carries the same current. Thus, ionizing a high velocity as that is strewing towards the work piece. The main advantage of this type is that the spot moves inside the wall and heat the incoming gas and outer layer remains cool. This type plasma has low thermal efficiency

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Base Metals

The base metals welded by plasma arc welding are

  1. Stainless steels
  2. Titanium alloys
  3. Carbon and low alloy steels
  4. Copper alloys
  5. Aluminium alloys

Types of Joint made in Plasma Arc Welding

The types of joint which are made by plasma Arc welding are

  1. Filler welds
  2. T-Welds
  3. Grooves
  4. Square groove

Advantages and Disadvantages of Plasma arc welding

The main advantage of plasma welding is that the control and quality finished in the part being welded. The torch design allows for improved control of the arc, along with a higher tolerance for in torch standoff distance. Welds are usually cleaner and smoother when using the PAW process. Smaller heat-affected zones result in welds that are very strong and less noticeable, which is important for some parts.

A major limitation in executing a plasma welding process is the relatively high startup costs. Plasma welding equipment tends to be expensive. Because it is a more focused welding process, the training and expertise mandatory is also more intense.

Applications of Plasma arc welding

  • It is in Aerospace applications.
  • It is used for melting high melting point metals
  • It is used for welding titanium plates.
  • It is used in welding nickel alloys.
  • It is used for tube mill applications.

1. Manufacturing Steel Tubes

Steel tubes are used extensively in the automobile industry as part of the exhaust system’s design. PAW is often used in the manufacturing industry since it:

  • Is much quicker than GTAW systems
  • It penetrates almost as well as
  • Reduces the amount of filler used

2. Welding Small Metal Components

With the keyhole setting offered on PAW systems, it is possible to operate on discrete components or produce small welds on bigger objects with more precision. Even on thicker steel products, it is capable of creating a firm seal in a single pass.

3. It’s the best for Butt joints

While laser beam welding is quicker than plasma arc welding, it has a lower tolerance for misalignment of the joints. GTAW systems produce high-quality welds, but they are inefficient and time-consuming to operate. Welders benefit from PAW because it increases their speed and their ability to produce good welds at joint locations.

4. Welding Electronic Chips That Are Too Thin

PAW has the ability to operate in a very low current mode, making it an excellent option for applications that include fragile computer components. Electronic chips may be susceptible to environmental conditions such as excessive heat, which is why low current is especially beneficial in certain application areas, as previously mentioned. However, for precision welds, PAW is the primary method of choice. GTAW and LBW are also sometimes utilised.

5. Manufacturing of medical devices

The use of excessive noise or heat in certain medical equipment might cause damage to the components that are sealed. Because of its high-precision operations and low dba output, PAW is an excellent choice for installing these components. Despite the fact that it is still somewhat loud at up to 100 dba during high-current operations, it is practically quiet while operating at lower currents.