Electron Beam welding
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Joined: Jun 2010
14-10-2010, 10:54 AM
Electron Beam welding.ppt (Size: 5.36 MB / Downloads: 444)
Electron Beam welding
Collaborative Project - IGCAR & DRDL
EB Welding of SS316 LN to SS316L(N)
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EB Welding of 9Cr-1Mo Steel to SS316L(N)
EB Welding of LAFM Steel to SS316L(N)
EB Welding Parameters
Joined: Apr 2012
22-08-2012, 04:53 PM
ELECTRON BEAM WELDING
ALL WELDING.doc (Size: 823 KB / Downloads: 42)
Electron beam welding is a radiant energy welding process in which the work pieces are joined by the heat obtained from a concentrated beam composed primarily of high-velocity electrons impinging on the surface to be joined.
The system consists of an electronic gun and a vacuum chamber inside which the work pieces to be joined are placed. The electronic gun emits and accelerates the beam of electrons and focuses it on the work pieces.
When a tungsten filament is electrically heated in vacuum to approximately 20000C it emits electrons. The electrons are then accelerated towards the hollow anode by establishing a high difference of voltage potential between the tungsten filament and a metal anode.
The electrons pass through the anode at high speeds (approximately half the speed of light), then collected into a concentrated beam and further directed towards the work piece with the help of magnetic forces resulting from focusing and deflection coils.
The highly accelerated electrons hit the base metal and penetrate slightly below the base surface. The kinetic energy of the electrons is converted into heat energy.
The succession of electrons striking at the same place causes the work piece metal to melt and fuse together.
It should be noted that, the greater the kinetic energy of the electrons, the greater is the amount of heat released. Since electrons cannot travel well through air, they are made to travel in vacuum which is the reason for enclosing the electron gun and the work piece in a vacuum chamber.
Advantages of Electron Beam Welding:
Any metals, including zirconium, beryllium or tungsten can be easily welded.
High quality welds, as the operation is carried in a vacuum.
Concentrated beam minimizes distortion.
Cooling rate is much higher.
Heat affected zone is less.
Shielding gas, flux or filler metal is not required.
Disadvantages of Electron Beam Welding:
High capital cost.
Extensive joint preparation is required.
Vacuum requirements tend to limit the production rate.
Size of the vacuum chamber restricts the size of the work piece being welded.
Not suitable for high carbon steels. Cracks occur due to high cooling rates.
ULTRASONIC BEAM WELDING
In Ultrasonic Beam welding ultrasonic waves are used as the energy source for welding. Ultrasonic waves are sound waves in the frequency range with 20KHz and more. These sound waves are above the human audible range. Ultrasonic welding is a solid state welding process.
Construction of Ultrasonic Beam Welding:
It consists of a power source and a transducer. The power essentially converts the mains frequency (50 KHz) to a very high frequency electric power. The transducer converts the power to magnetic flux and then the kinetic motion is amplified through a velocity transformer. The assembly of transducer and velocity transformer is called as “sonotrode”. The tip of the velocity transformer is made of low high speed steel or nimonic (Niialloy). The velocity transformer is made of low loss and high strength metal such as Titanium. The work to be welded is placed on the anvil and below the tip. Load is applied on the tip. Due to ultrasonic vibrations the oxide layer on the metal surfaces is broken and a clear surface results. The temperature at the interface of the work rises to 35-50% of the melting point of the work and a solid joint is achieved.