Laser Beam Welding – Equipment, Principle, Working with Advantages and Disadvantages

Laser Beam Welding is a fusion welding process in which two metal pieces are joined together by the use of laser. The laser beams are focused to the cavity between the two metal pieces to be joined. The laser beams have enough energy and when it strikes the metal pieces produces heat that melts the material from the two metal pieces and fills the cavity. After cooling a strong weld is formed between the two pieces.

It is a very efficient welding process and can be automated with robotics machinery easily. This welding technique is mostly used in automotive industry.

Working Principle

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

The main parts or equipment of laser beam welding are:

  1. Laser Machine: It is a machine that is used to produce laser for welding. The main components of laser machine are shown below.
  2. Power Source: A high voltage power source is applied across the laser machine to produce laser beam.
  3. CAM: It is a computer aided manufacturing in which the laser machine is integrated with the computers to perform 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: Electron Beam Welding Process – Equipments, Working Principle with Diagram

Types of Laser Used

  1. Gas lasers: It uses mixtures of gases as lasing medium to produce laser. Mixtures of gases such as nitrogen, helium and co2 are used as lasing medium.
  2. Solid-state laser: it uses several solid media such as synthetic ruby crystal (chromium in aluminum oxide), neodymium in glass (Nd:glass), and neodymium in yttrium aluminum garnet (Nd-YAG , most commonly used).
  3. Fiber laser: The lasing medium in this type of laser is optical fiber itself.

Characteristics of Laser Beam Welding

  1. The power density of laser beam welding is high. It is of the order 1 MW/cm2. Because of this high energy density, it has small heat-affected zones. The rate of heating and cooling is high.
  2. The laser beams produced are coherent ( having same phase) and monochromatic ( i.e. having same wavelength).
  3. It is used to weld smaller sizes spot but the spot sizes can vary from .2mm to 13 mm.
  4. The depth of penetration of the LBW depends upon the amount of power supply and location of the focal point. It is proportional the amount of power supply. When the focal point is kept slightly below the surface of the workpiece, the depth of penetration is maximized.
  5. Pulsed or continuous laser beams are used for welding. Thin materials are weld by using millisecond-pulses and continuous laser beams are used for deep welds.
  6. It is versatile process because it is capable of welding carbon steels, stainless steel, HSLA Steels, aluminum and titanium. Due to high cooling rate, the problem of cracking is there when welding high-carbon steels.
  7. It produces high quality weld.
  8. This welding process is most popular in automotive industry.

Working

Laser Beam Welding

  • First the setup of welding machine at the desired location (in between the two metal pieces to be joined) is done.
  • After setup, a high voltage power supply is applied on 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.
  • This high concentrated laser beam is focused to the desired location for the welding of the multiple pieces together. Lens are 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.
  • 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.
  • This is how a laser Beam Welding Works.

Advantages

  • It produces high weld quality.
  • LBW can be easily automated with robotic machinery for large volume production.
  • No electrode is required.
  • No tool wears because it is a non-contact process.
  • The time taken for welding thick section is reduced.
  • It is capable of welding in those areas which is not easily accessible.
  • It has the ability to weld metals with dissimilar physical properties.
  • It can be weld through air and no vacuum is required.
  • X – Ray shielding is not required as it does not produce any X-Rays.
  • It can be focused on small areas for welding. This is because of its narrower beam of high energy.
  • Wide variety of materials can be welded by using laser beam welding.
  • It produces weld of aspect ratio (i.e. depth to width ratio) of 10:1.

Disadvantages

  • Initial cost is high. The equipment used in LBW has high cost.
  • High maintenance cost.
  • Due to rapid rate of cooling, cracks may be produced in some metals.
  • High skilled labour is required to operate LBW.
  • The welding thickness is limited to 19 mm.
  • The energy conversion efficiency in LBW is very low. It is usually below 10 %.

Application

The laser beam welding is dominant in automotive industry. It is used in the area where large volume production is required.

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