Electron Beam Welding | Friction Welding | Diffusion Welding

ELECTRON BEAM WELDING

Principle

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

01 - ELECTRON BEAM WELDING - TYPES OF WELDING

Working

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 1mm 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

Principle

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.

01 - FRICTION WELDING - TYPES OF WELDING PROCESS

Working

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.

01 - DIFFUSION WELDING - TYPES OF WELDING PROCESS

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.

Thermosetting Plastics | Various Types of Thermosetting Plastics

Thermosetting Plastics

The plastic which are hardened by the heating is called as thermo setting plastic. this heating reaction is non-reversible.

The molecules of this type of plastic have a very strong binding force. The raw material for these kinds of plastics is available in liquid or solid form. These types of plastics consume more time for polymerization

Phenol formaldehyde

01 - THERMOSETTING PLASTICS - PHENOL FORMALDEHYDE

It is also called as bakelite. It is obtained by the reaction of phenol with formaldehyde. It is generally dark in color and has high strength, stability, and rigidity. It is easy to handle while casting. It is mainly used for making plugs, knobs, pulleys, bottle caps, tooling, etc.

Polyster resin

01 - THERMOSETTING PLASTICS - POLYSTER RESIN

Polyster resin has low moisture and has very good electrical resistance. It is available in variety of colors. It is generally used to manufacture paper mat, TV parts and car bodies. Main drawback of this plastic is high cost.

Melamines

01 - THERMOSETTING PLASTICS - MELAMINES

It has very good electrical and heat resistance. This melamines has good stability and low moisture absorption. Melamines are also called as melmac, melantine and plaskon. It is widely used moulded parts. It is generally used for making telephone sets, circuit breakers, switch panels and lighting fixtures.

Phenol furfural

01 - THERMOSETTING PLASTICS - PHENOL FURFURAL

It has good flowability at low moulding temperatures and sets quickly at correct temperatures. The phenol furfural has good resistance to moisture and electricity. Generally used for manufacturing brake linings, electrical parts and instrument cabinets.

Epoxy resins

01 - THERMOSETTING PLASTICS - EPOXY RESINS

The popular variety of epoxy resin is araldite. It has very good electrical and chemical resistance. It is generally available in the form of liquid. It has good resistance to wear and impact. The only disadvantage is that it is expensive. Tools and dies, jigs and fixtures, housing

Silicones

01 - THERMOSETTING PLASTICS - SILICONES

The main property of silicone is that it has a high resistance to withstand high temperature of up to 260°C and possess excellent dielectric strength at high temperatures. It is also used as water repellant in liquid state. These silicones can be compressed reinforced. It is generally used in coating, laminates, foam products and induction heating process.

Urea formaldehyde

01 - THERMOSETTING PLASTICS - UREA FORMALDEHYDE

It is obtained by the condensation of urea and aqueous formaldehyde. It cannot be cast but can withstand temperatures up to 77°C. It is generally used as adhesive and binding material. It is generally used is table ware, buttons, clock cases etc.

Alkyds

01 - THERMOSETTING PLASTICS - ALKYDS

It is also known as oil-modified polyester. Alkyds are used in synthetic enamels and lacquers. It is used in solid from where high electrical and heat resistance are required. Used in manufacturing automobile parts.

Polyurethanes

01 - THERMOSETTING PLASTICS - POLYURETHANES

It is mainly used for cushion in transportation seats for insulation and electronic equipment as a packing material.