In laser welding we must distinguish between two main processes: thermal conductivity welding and deep penetration welding. In thermal conductivity welding, the materials to be joined melt as a result of absorption of the laser beam on the surface of the material, and the associated conduction of heat. The solidified smelt joins the materials. The depth of the weld in this process is typically < 1 mm.

Deep penetration welding, which begins at an energy density of approx. 106 W per cm2, is based on the creation of a vapor capillary in the material. To achieve this, it is necessary to heat the material locally to its evaporation point. The resulting vapor pressure in the material creates a capillary approx. 1.5 times the diameter of the focal spot of the laser beam, which is moved through the material by the movement system, following the contour to be welded. The hydrostatic pressure, the surface tension of the smelt, and the vapor pressure in the capillary compensate each other, so that the capillary (often referred to as the "keyhole") does not collapse. The total reflection within the keyhole guides the applied laser beam deep into the material, in such a way that today, given sufficient laser power, weld depths of up to 25 mm (steel) can be achieved.

Steels and aluminum are the classic area for laser welding. But in principle, all materials that can be welded using traditional methods can also be welded with lasers, often at higher speed and quality compared with the traditional processes.

Laser Surfacing