Laser Welding Explained: Techniques, Types, and Industrial Applications

What is Laser Welding?

Laser beam welding (LBW) is a welding technique used to join pieces of metal or thermoplastics through the use of a laser. The beam provides a concentrated heat source, allowing for narrow, deep welds and high welding rates. It is based on keyhole or penetration mode welding.

Laser welding operates in two fundamentally different modes: conduction limited welding and keyhole welding. The mode in which the laser beam will interact with the material it is welding will depend on the power density across the beam hitting the workpiece.

The processes are frequently used in high-volume applications using automation, as in the automotive industry. The main advantage of laser welding, due to its high energy density, is its ability to melt the area located at the edges of the joint, without affecting a large area of the part.

Laser 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. Furthermore, laser welding can be performed “out of a vacuum” and the fiber-optic delivery of near-infrared solid-state laser beams provides increased flexibility compared with other joining technologies.

Equipment of Laser Beam Machine

The main parts or equipment of laser beam welding are:

• Laser Machine: It is a machine that is used to produce a laser for welding. The main components of the laser machine are shown below.
• Power Source: A high voltage power source is applied across the laser machine to produce a laser beam.
• 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.
• 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.
• Shielding Gas: A shielding gas may be used during the welding process in order to prevent the w/p from oxidation.

How do Laser Beam Welding Work?

Laser welding is a process used to join together metals or thermoplastics using a laser beam to form a weld. Being such a concentrated heat source, in thin materials laser welding can be carried out at high welding speeds of meters per minute, and in thicker materials can produce narrow, deep welds between square-edged parts.

The laser beam welding works on the principle that when the electrons of an atom are excited by receiving some energy. And then after some time when it returns to its ground state, it emits a photon of light.

The concentration of this emitted photon is increased by the excited emission of radiation and we get a high-energy focused laser beam. The light amplification by stimulated emission of radiation is named a laser.

Initially, the welding machine is set up (between the two metal pieces to join) at the desired location. Later setup, a high voltage power supply is applied to the laser machine to perform an operation.

The lens is used to focus the laser into the area where welding is required. CAM is used to control the speed of the laser and workpiece table during the welding process.

It starts the machine’s flash lamp and it emits light photons. The energy of light photons is absorbed by the atoms of ruby ​​crystals and electrons are excited to their higher energy levels. When they return to their low energy state or ground state, they emit a photon of light.

This light photon again stimulates the electrons of the atom and produces two photons. This process continues and we get a focused laser beam that is used on the desired location for welding multiple pieces together.

Types of Lasers Used

1. Gas lasers: It uses mixtures of gases as a lasing medium to produce laser. Mixtures of gases such as nitrogen, helium, and co2 are used as the 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.

Advantages of Laser Beam Machine

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

• Weld strength: The laser weld is narrow with an excellent depth-to-width ratio and higher strength.
• Heat affected zone: The heat affected zone is limited, and due to rapid cooling, the surrounding material is not annealed.
• Metals: Lasers successfully weld carbon steel, high strength steel, stainless steel, titanium, aluminum, and precious metals as well as dissimilar materials.
• Precision work: The small, tightly controlled laser beam permits accurate micro-welding of miniature components.
• Deformation: Parts have minimal deformity or shrink.
• No contact: No physical contact between the material and laser head.
• One sided welding: Laser welding can replace spot welding requiring access from one side only.
• Scrap: Laser welding is controllable and generates low volumes of scrap.

Disadvantages of Laser Beam Machine

• The welding equipment is expensive so the cost for this process is high.
• If the filler material is necessary but, in this process, limited amount produced with the use of filler material so relatively expensive.
• There are also a few post welding operations.
• Joints must be accurately positioned laterally under the beam.
• The final position of the joint is accurately aligned with the beam impingement point.
• The maximum joint thickness that can be welded by laser beam is somewhat limited.
• The materials have high thermal conductivity and reflectivity like Al and Cu alloys can affect the weldability with lasers.
• An appropriate plasma control device must be employed to ensure the weld reproducibility while performing moderate to high power laser welding.
• Lasers tend to have low energy conversion efficiency less than 10 percent.
• Some weld-porosity and brittleness can be expected, as a consequence of the rapid solidification characteristics of the LBM.

Application of Laser Beam Machine

• It is prominent in the automotive industry. So, it is used in the area where large volume production is required.
• It is employed for high precision welds. As it does not use any electrode, the final weld will be light but strong.
• The laser welding is also frequently used in making of jeweler.
• However, laser beam welding is used in medical industries to hold metals together on a small scale.