Laser Beam Welding

The term laser (an acronym for Light Amplification by Stimulated Emission of Radiation) refers to the mechanism for generating electromagnetic radiation, normally between the ultraviolet and infra-red frequencies of the electromagnetic spectrum, by the process of stimulated emission.

Laser beam welding is a high-power-density fusion-welding process that produces high aspect ratio welds with a relatively low heat input compared with arc-welding processes. Laser beam welding can be performed ‘out of vacuum’.

It can also be understood like laser beam welding (LBW) is a welding process that produces coalescence of materials with the heat obtained from the application of a concentrate coherent light beam impinging upon the surfaces to be joined.

Laser welding is predominantly  used for the production of metallic aerospace components for high-performance environments.

Also read: Shell Mould Casting, Cold Welding

Laser Beam Welding Process (Mechanics)

1.Interaction of laser beam with work material.

2.Heat conduction and temperature rise.

Melting vaporization and joining : When using the laser beam for welding, the  electromagnetic radiation impinges on the surface of the base metal with such a  concentration of energy that the temperature of the surface is melted vapor and melts metal below.

Working Principle of Laser Beam Welding

It works on the principle that when electrons of an atom gets excited by absorbing some energy. And then after some time when it returns back to its ground state, it emits a photon of light. The concentration of this emitted photon increased by stimulated emission of radiation and we get a high energy concentrated laser beam.

Light amplification by stimulated emission of radiation is called laser.

Main Parts of Laser Beam Welding

The main parts or equipment of laser beam welding are:

1. Laser Machine: Used to produce a laser for welding. 
2. Power Source: A high voltage power source is used to produce a laser beam.
3. CAM: It is a computer-aided manufacturing in which the laser machine is integrated with the computers to perform the welding process. All the controlling action during the welding process by laser is done by CAM. It speeds up the welding process to a greater extent.
4. CAD: It is called as Computer-aided Design. It is used to design the job for welding. Here computers are used to design the workpiece and how the welding is performed on it.
5. Shielding Gas: A shielding gas may be used during the welding process in order to prevent the w/p from oxidation.

Also read: Sand Mould Casting, Submerged-Arc welding (SAW)

Types of Lasers

The primary types of lasers used in welding and cutting are:

• Gas lasers: use a mixture of gases such as helium and nitrogen. There are also CO2 or carbon dioxide lasers. These lasers use a low-current, high-voltage power source to excite the gas mixture using a lasing medium. Operate in a pulsed or continuous mode.
  Carbon dioxide lasers use a mixture of high purity carbon dioxide with helium and nitrogen as the lasing medium. CO2 lasers are also used in dual-beam laser welding where the beam is split into two equal power beams.
• Solid state lasers: (Nd:YAG type and ruby lasers) Operate at 1micrometer wavelengths. They can be pulsed or operate continuously. Pulsed operation produced joints similar to spot welds but with complete penetration. The pulse energy is 1 to 100 Joules. Pulse time is 1 to 10 milliseconds.
• Diode lasers

Working of Laser Beam Welding

1. First, the setup of welding machine at the desired location (in between the two metal pieces to be joined) is done.
2. After setup, a high voltage power supply is applied to the laser machine. This starts the flash lamps of the machine and it emits light photons. The energy of the light photon is absorbed by the atoms of ruby crystal and electrons get excited to their higher energy level. When they return back to their ground state (lower Energy state) they emit a photon of light. This light photon again stimulates the excited electrons of the atom and produces two photons. This process keeps continue and we get a concentrated laser beam.
3. This high concentrated laser beam is focused to the desired location for the welding of the multiple pieces together. Lens is used to focus the laser to the area where welding is needed. CAM is used to control the motion of the laser and workpiece table during the welding process.
4. As the laser beam strikes the cavity between the two metal pieces to be joined, it melts the base metal from both the pieces and fuses them together. After solidification, we get a strong weld.
5. This is how a laser Beam Welding Works.

Also read: Electron Beam Welding, Plasma Arc Welding (PAW)

Advantages of Laser Beam Welding

1. Works with high alloy metals without difficulty
2. Can be used in open air
3. Can be transmitted over long distances with a minimal loss of power
4. Narrow heat affected zone
5. Low total thermal input
6. Welds dissimilar metals
7. No filler metals necessary
8. No secondary finishing necessary
9. Extremely accurate
10. Produces deep and narrow welds
11. Low distortion in welds
12. High quality welds
13. Can weld small, thin components
14. No contact with materials

Limitations of Laser Beam Welding

1. Rapid cooling rate may cause cracking in some metals
2. High capital cost for equipment
3. Optical surfaces of the laser are easily damaged
4. High maintenance costs