What Is Laser Welding?- Working, Types And Application

What is Laser Welding?

Laser beam welding (LBW) is a welding technique where some type of laser is used to melt and unite pieces of metal (or thermoplastics).

The laser beam is a concentrated heat source and as such, LBW can produce narrow, deep welds at high welding rates. In LBW usually keyhole or penetration mode welding is typically employed.

Laser welding can be accomplished in two distinct operating modes, conduction-limited welding and keyhole welding. The operating mode in which the laser beam will interact with the material to be welded will depend on the power density emitted from the beam striking the workpiece.

Often these processes are used in high volume applications with some sort of automation, think automotive. The primary benefit of laser welding, being a process with a higher energy density than other processes, is that the welding will happen with just melting of the part along the edges of the joint, so that the heat will not affect a large area of the part.

Laser welding is a high-power density fusion-welding process that produces high aspect ratio welds with a lower heat input than a number of arc-welding process.

In addition to the above, laser welding can take place “out of a vacuum” and the fiber-optic delivery of near-infrared solid state laser beam allows for greater flexibility than the joining processes mentioned above.

Equipment of Laser Beam Machine

The main parts or equipment of laser beam welding are:

• Laser Machine: A machine which is employed to develop a laser for the use in welding. The basic components of the laser machine are shown below.
• Power Source: A high voltage power source is applied across the laser machine to generate the laser beam.
• CAM: The laser machine is integrated with computers in a CAM situation (which stands for computer-aided manufacturing). The CAM program facilitates all of the controlling action during the actual welding process by laser. This also is used to significantly speed up the welding process.
• CAD: Computer-aided Design is defined as CAD. This is used to design the workpiece for welding. Computers are used in the design of the workpiece and the way in which to perform the welding operation.
• Shielding Gas: A shielding gas may be used during the welding process to protect the w/p from oxidation.

How do Laser Beam Welding Work?

Laser welding is a method of joining metals and thermoplastics using a concentrated laser beam to create a weld.

Due to being a highly concentrated heat-energy source, laser welding can be carried out quickly in thin materials at a rate of meters per minute and can also develop deep, narrow welds in thick materials, joining square edge parts.

The laser beam works on the principle that electrons of an atom can become excited when energy is supplied to them. Once the electrons return to their normal energy levels, they emit energy in the form of a photon of light.

To amplify and concentrate the photon’s emitted energy from electrically exciting the electron state of the atom into a high-energy concentrated laser beam, we name the amplification of light from excited, stimulated emissions of radiation, that is, also called laser.

The welding machine is to be firstly setup (between the two metal pieces to join) to the specified location. After the location setup, the laser machine will have the high voltage power applied to it to operate.

A lens is used to focus the laser into the area to be welded. Computer Aided Manufacturing (CAM) supports controlling the speed of the laser and workpiece table in the welding operation.

The CAM starts the flash lamp of the laser machine and the flash lamp emits light photons. The energy of the light photons is absorbed by the atoms in ruby crystals and electron energy levels are excited to higher energy levels. When these electrons return to their normal, low energy state (ground), they emit a photon of light.

The emitted light photon then excited the electron energy levels again and resulted in the production of two photons. This process of exciting the electrons continued and we have a laser beam that is concentrated on the specified area to weld metal together.

Types of Lasers Used

1. Gas lasers: They utilize gas mixtures as a lasing medium to produce a lasing process. Mixtures of gases consisting of nitrogen, helium, and CO₂ are used as the lasing media.
2. Solid State laser: it uses several solid media such as ruby crystal (chromium in aluminum oxide), neodymium in glass (Nd: glass), and neodymium in yttrium aluminum garnet (Nd-YAG which is the most common).
3. Fiber laser: The laser medium is the optical fiber itself.

Advantages of Laser Beam Machine

Precise control of the laser beam offers users several benefits over TIG, MIG, and spot-welding:

• Weld quality: The weld made by laser has a narrow bead width, an excellent depth to width ratio, and is stronger.
• Heat-affected zone: The heat-affected zone is small, with the rapid cooling of the welded metal preventing annealing of the surrounding material.
• Metals: Lasers can weld carbon and high-strength steel, stainless steels, titanium, aluminum, and precious metals as well as dissimilar materials.
• Precision work: The small beam of light with a small diameter and well-defined edges allows controlled micro-welding of very small parts.
• Deformation: Parts have very limited deformation or shrinkage.
• No contact: No contact is made with the material through means of the laser head.
• One-sided welding: Laser welding eliminates some of the need for access to both sides of some spot welding applications.
• Scrap: Laser welding is controllable with much less scrap generated.

Disadvantages of Laser Beam Machine

• The welding apparatus is costly and therefore the overall costs associated with this process are expected to be high.
• If filler material is required in this process, a small amount is produced with filler so more costly.
• There will also be a few post-welding processes.
• The joints will need to be set accurately laterally under the beam.
• The final position of the joint is vertically aligned under the point of the beam impingement.
• The maximum joint thickness that can be welded by a laser beam has some limitations.
• The weldability of certain materials, of high thermal conductivity and reflectivity, such as Al and Cu alloys, can be restricted by laser.
• An appropriate plasma control device should be used to ensure weld reproducibility at moderate to high laser welding power.
• Lasers appear to have a low energy conversion efficiency of less than ten percent.
• Some weld-porosity and brittleness may occur due to the rapid solidification rates associated with the LBM.

Application of Laser Beam Machine

• It’s commonly found in automotive manufacturing. Therefore, it’s used in applications with high-volume production.
• It is being used for welds that require high precision. Because it does not use an electrode, the finished weld will be light but offer high strength.
• LASER welding is also very often used in the manufacturing of jewelry.
• Despite this, laser beam welding is used in the medical industry to join together metals on a smaller scale.

FAQs