Laser beam welding with mobile vacuum: MoVac

Abstract

Laser beam welding in vacuum (LaVa) is a process modification of laser beam welding that combines the advantages of laser and electron beam. Due to the reduced pressure, the evaporation temperature of Aluminum and Iron decreases. by approx. 1000 K. As a result, the penetration depth can be significantly increased compared to conventional laser beam welding, while maintaining the same beam power. State of the art research shows that previously unattainable penetrations depths of up to 80 mm can be achieved in steel. Up to now, laser beam welding in vacuum has been a stationary process and was bound to vacuum chambers. However, since high penetration depths usually involve large components, the great potential in the thick plate metal sector could not be exploited. Therefore, laser beam welding with mobile vacuum was developed, where a small vacuum chamber is moved alongside the welding process so that the vacuum is generated locally around the weld bath. A dynamic seal is installed between workpiece and mobile vacuum chamber, so that a pressure of approx. 10 - 20 mbar can be generated, which is sufficient for the process. Current investigations show that steel plates with a thickness of 40 mm can be joined in one layer with only 12 kW beam power. Furthermore, the process shows a high tolerance for edge offsets and gaps. In the latter case, filler material is used to bridge gaps larger than 0.5 mm.