Laser welding processes

Laser welding processes

Laser welding is a welding process that utilizes concentrated high-power laser light to melt the material. An important aspect of this is that the light is absorbed by the material, creating heat within it and forming a molten pool. Not all materials absorb light of a certain wavelength equally well. The degree of absorption depends on the wavelength of the laser light and the type of material.

There are different forms of laser welding:

  • Conductive welding
  • Laser keyhole welding
  • Laser hybrid welding
  • Remote welding
  • Manual laser welding

Conductive Welding

Conductive laser welding is characterized by limited penetration. This type of laser welding process is primarily used for thin plate thicknesses where the appearance of the weld is crucial. Compared to arc welding processes, conductive welding offers a high degree of precision and can be applied for high-precision welding tasks.

Laser Keyhole Welding

Laser keyhole welding is employed for thicker materials. The lasers used for this process have high power. A keyhole forms as vapor develops and expands within the material. As a result, the laser light can penetrate deeper into the material, achieving greater depth with the laser.

Weld seams for keyhole welding need to be meticulously prepared. Because the penetration is deep and narrow, welding can be performed with a seam preparation that doesn’t require the addition of material.

Laser Hybrid Welding

In laser hybrid welding, the laser is combined with the MIG/MAG welding process. By integrating both welding processes, it’s possible to achieve high welding speeds with significant penetration depth. Because material is also added in this process variant, it can accommodate larger tolerances.

Furthermore, in laser hybrid welding, it’s possible to generate a slight overthickness, which can be challenging with keyhole welding due to the lack of added material.

Remote welding

Remote laser welding involves projecting the laser beam onto the material to be welded from a distance. The laser beam is directed by moving optics within the welding head. This technique allows for very high welding speeds to be achieved. It also provides opportunities for welding hard-to-reach weld seams. The welding head can be placed in machines with a fixed head arrangement or carried by a robot. By combining it with a scanner, the welding head can quickly identify and weld seams.

Manual Laser Welding

Manual laser welding has been increasingly applied since its introduction to the market in 2019/2020. With the introduction of hand guns equipped with a wobble function, it has become possible to effectively control the molten pool. This allows for the creation of a molten pool that is large enough for welding.

Unlike other laser welding processes, there is no shielding between the welding process and the operator in manual laser welding. Working with a manual laser welding machine requires good safety measures and instructions. Nevertheless, this welding process can be performed safely when the right precautions and provisions are taken.

The necessary steps for safely applying manual laser welding include:

  • Work with a safe machine.
  • Work in a shielded area.
  • Establish clear work agreements/processes.
  • Use the appropriate protective equipment, including laser safety glasses.

Many of these measures are prescribed in European standards.

In general, it is important to note that all laser welding processes typically have lower heat input compared to arc welding processes. This is due to the often much higher welding speed and the smaller molten pool compared to arc welding processes.

Laser Sources for Laser Welding

Various types of laser sources are used for laser welding, including:

  • Disk lasers
  • Fiber lasers
  • Diode lasers
  • CO2 lasers

Disk Lasers

A disk laser is a solid-state laser that incorporates a thin layer of ytterbium as the laser medium. Laser light can be transported to the optics of the welding head through a fiber, allowing for robotic welding.

Fiber Lasers

Fiber lasers also utilize ytterbium as the laser medium. In fiber lasers, the medium is used as a “dope” in the core of the fiber. Laser diodes in the machine activate the medium in the fibers. Fiber laser welding machines typically operate at a wavelength ranging from 1020 nm to 1080 nm. This wavelength is well-absorbed by materials like steel, stainless steel, and can also be used for welding aluminum.

Diode Lasers

Diode lasers are solid-state lasers used for welding highly reflective materials. Since many of these materials do not absorb the wavelengths of a fiber laser well, diode lasers with wavelengths better absorbed by the material can be used as an alternative.

CO2 Lasers

CO2 lasers use a gas mixture as the laser medium. This type of laser source is becoming less common in welding applications due to the emergence of high-power fiber lasers. An important drawback for welding applications is that the laser beam from a fiber laser can only be guided with mirrors.

Consequently, the laser beam cannot be used for robotic applications.