Metal welding

The process of laser welding involves one of two different processes:

Fusion welding (also called melt welding),
and keyhole welding.

Fusion welding

The material only melts on the surface.

In fusion welding, the materials to be joined are melted through absorption of the laser beam on the surface of the material. The melted sections flow into each other and the combined melted section hardens to join the materials. This process is used to join parts with thin walls. The welding depth is typically < 1 mm.
The laser produces a smooth, well rounded welding seam that requires no further processing.

Keyhole welding

The principle of keyhole welding is based on producing a vapour capillary. The laser beam produces the required local evaporation temperature. The evaporation pressure produced in the material generates a capillary with a diameter about 1.5 times that of the laser beam focus.

This evaporation capillary (also called a keyhole) is drawn through the workpiece by the movement system of the laser machining system. The metal fusion flows around the evaporation capillary and hardens on the back. A deep, narrow welding seam with a uniform joint is produced.

Keyhole welding has a high efficiency level and can be performed at high welding speeds. Thanks to the high speed, the area affected by heat is small and the warpage in material is slight. The process is used when high welding depths are required or several layers of material must be welded at a time.