Electron Beam Welding | Friction Welding | Diffusion Welding

ELECTRON BEAM WELDING

Electron beam welding (EBW) is a thermal cutting method in which high-velocity electrons condensed into a narrow beam are used to heat, melt, or vaporise the material in a short period of time. A variety of applications, including drilling, cutting, annealing, and welding, rely on this process to function properly.

Principle of Electron Beam Welding

Beam of electron is used for producing high temperatures and melting the work piece to be welded.

Working of Electron Beam Welding

When tungsten filament is electrically heated in vacuum, it will emit the electrons. These electrons carry a negative charge which is passed through the anode hole. The electron beam is focused by the focusing lens. When the focused electron beam strikes the work piece, the kinetic energy of this electron beam is converted into heat energy.

This heat energy is used to weld the metals. The operation is carried out in vacuum. So, it is possible to weld holes. The beams are focused about 0.25 to 1 mm diameter and power density of 10kW/mm aluminium material having focusing length of about 40mm and steel about 30mm.

The variables which are controlled in the electron beam welding are

1. Voltage

2. Speed

3. Distance between beam gun to work piece

FRICTION WELDING

Friction welding is believed to be one of the quickest welding technologies available, with speeds that may be up to twice or even 100 times quicker than traditional fusion welding. It does not need extensive surface preparation.  Friction welding may be used to connect surfaces that have been machined, saw cut, or sheared.

It is a kind of solid-state welding method in which heat is created by mechanical friction between a moving component and a stationary component while at the same time a lateral force known as “upset” is provided to the components in order to plastically displace and fuse the materials.

In the manufacturing industry, friction welding may provide several solutions to difficult production difficulties. Friction welding is a time- and cost-effective method of producing new components because of its many benefits, which include uniform quality, the ability to link diverse metals together, and decreased material waste.

The following materials are welded using this welding process: aluminium, magnesium, copper and copper alloys, hafnium and zirconium, inconel and superalloys, stainless steel and ferrous alloys, titanium, and dissimilar materials.

Friction welding is a technique that may be used to improve the quality of industrial rollers, tubes, and shafts. Industrial printers, material handling equipment, as well as automotive, aerospace, marine, and oil applications, are often manufactured using this technology.

Principle of friction welding

It is a solid state welding process wherein coalescence is formed by the heat which is obtained from mechanically induced sliding motion between rubbing surfaces.

Working of friction welding

Initially, the components to be welded are held under pressure. One part is rotated at high speed and other part is held stationary. In this welding, the movable clamp is moved and contacted with the rotating component. The heat is produced between contact surfaces. This heat is used to weld the components under pressure. The pressure during welding may be about to few Mpa.

During this period, metal is slowly extruded from the weld region to form on upset For stopping the relative motion, the brake system is applied.

Parameters which are considered in friction welds are

1. Friction Pressure
2. Speed
3. Burn off

The materials that can be welded are listed below

1. Brass of Bronze
2. Nickel
3. Titanium alloys
4. Stainless steel
5. Aluminium & Aluminium alloys

The basic joints are made by friction welding as follows

1. Bar-belt joint
2. Bar-ball joint
3. Tee-butt joint

DIFFUSION WELDING

It is a solid state joining process in which the strength of the joint results primarily from diffusion. This process requires temperature of about 0.5 in order to have a high diffusion rate between the parts being joined. The strength of the welding depends on pressure, temperature, time of contact and the Cleanliness of the metal. The example for diffusion welding is bonding of gold over copper. First, a thin layer of gold foil is obtained by hammering. The gold is then located over copper and then weight is placed on top of it. The assembly is then placed in a furnace and left until a good bond is obtained.

Generally in diffusion welding, pressure may be applied by dead weight or a by a press using differential gas pressure. The parts are usually heated in a furnace or by electrical resistance. The diffusion welding is suitable for dissimilar metals. It is also used in reactive metals like titanium, zirconium and refractory metal alloys. The diffusion welding process is very slow when compare to other welding process.