Page 226 - CITS - Welder - Trade Theory

WELDER - CITS

Fig 3

Electron beam welding equipment’s
An Electron Beam Welding machine consists basically of the following components:
1 Electron Beam Gun

(a. Tungsten Filament b. Anode c. Cathode and d. Focusing Coil)
2 A vacuum chamber
3 A transport system
Electron beam gun

Most electron beam guns used are the triode type. It consists of a) Tungsten Filament b) Anode c) Cathode and d)
Focusing Coil. The Tungsten Filament units’ electrons when it is heated in vacuum chamber to 2000°C. Electrons
carry a negative charge and are repelled by the cathode electrode and are made to pass through the central hole
of the anode (+). The electrons are greatly accelerated by the potential differences between anode and cathode.
Then, the beam is focused by a lens. (Electromagnetic Focusing Coil) The purpose of the electron into a narrow
beam.
Vacuum chamber
The vacuum chamber is operated in conjunction with pumps and a pumping system to control the vacuum
environment. The size and design of the vacuum chamber used in electron beam welding will depend on the
dimensions of the weldment.

Transport system
Each machine is equipped with some form of transfer sys- tem to provide movement for the gun and work. These
systems are usually driven by DC motors, which control position, Location and Velocities of both the gun and the
work.
Description of equipment and welding procedure Fig 4 shows an electron beam welding equipment/setup.
The machine has a chamber in which a filament is used.
This filament emits (gives off) a stream of electrons. These electrons from the emitter passes through an anode,
column valve, diaphragm and then passes through an electromagnet called magnetic lens. This magnetic lens
is used to focus the high energetic electron beam which also possesses a high heat intensity. The work piece
to be welded is kept in a vacuum chamber below the magnetic lens. The electron beam can be directed either
downwards or deflected in any other direction within the vacuum chamber by using deflection coils. The welding is
done in a vacuum chamber because the air if present will interfere with the electron beam and affect the welding
action. Also the vacuum acts as a shield against radiation hazards. The heat energy required to melt the base
metal is controlled by the current in the electron gun filament. The operator/ welder can watch the welding area

213

CITS : C G & M - Welder - Lesson 77 - 82