Page 224 - CITS - Welder - Trade Theory

WELDER - CITS

MODULE 8 : Advance Welding & Cutting

Lesson 77- 82 : Principles and applications of Laser

welding, Electron beam welding

Objectives

At the end of this lesson you shall be able to
• describe the principal of laser welding
• explain the equipment of laser welding
• explain the electron beam welding.

1 Laser welding
Laser is the acronym for Light Amplification by Stimulated Emission of Radiation. Laser Welding is a method in
which work piece is melted and joined by narrow beam of intense Monochromatic Light. (Laser Beam) When the
beam strikes the job, the heat produced melts and fuses even the hardest materials. (Fig 1)

Fig 1

Process:
Electrical energy stored in a capacitor bank is discharged into a flash lamp. The stimulating light source usually in
a linear arc discharge lamp such as Zeon, Argon, or Krypton gas flash lamp. When the flash lamp fires, and then
is a powerful burst of light that pumps electrons with the light emitted (Ruby Rod) to higher than normal energy
levels. The light emitted by ruby rod is in pulse and is of single wave length travelling parallel to ruby rod. The
mirrors are provided to reflect the light coming to the ends of ruby rod. So that light may pass back through the
ruby rod increasing the energy level of electrons further to emit Laser Beam.

It goes through a focusing device where it is pin pointed on the work piece. Fusion takes place and the weld is
accomplished. There are three basic types of Lasers.
a The solid laser

b The gas laser and,
c The semi-conductor.
The type of Laser depends upon the lasing source. The Solid Laser some type of crystal such as the Ruby or the
Sapphire used for its lasing ability

The gas laser consists of a gas (Carbon Di-oxide, Xenon) or a mixture of gases (90% Helium, 10% Neon)
contained in a glass tube with highly polished mirrors at each end. One of the most widely used Gas Laser is CO2
Laser. The radiant energy density of the CO2 Laser is greater than that of the sun.

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