Main fields of work

Joining techniques constitutes the focus of this group. This includes welding as well as brazing with laser beams. Here, mixed compounds of different metal tapes are in the center. This refers mainly to aluminum with other joining partners. Yet, also application in the high-power area of more than 10 kW laser output are a focus of the group. Here, an emphasis is put on steel and aluminum. For these materials the process limits of laser- MIG-hybrid-welding are being extended and the industrial application is being advanced. In the same way, lasers with low output powers are interesting for many SMEs when talking about fine welding. Pulsed and continuous wave systems are able to cover the area of foils with 50 μm and components up to 5 mm.

Current scientific activities and focuses

In 2009 projects focused on mixed compounds, thick sheets and thin steel sheets. The BMBF project HYBRILAS deals with the welding of steel sheets with a thickness of more than 20 mm and aluminum sheets with a thickness up to 15 mm. In order to achieve these goals, a 16kW disk laser is applied, which is combined with two power sources with 500 A welding current each. Due to an adjusted alignment of the laser as the power sources within the joining zone, a high feed rate and a high gap-bridging ability can be achieved. In the center of the research project are pipeline constructions as well as application in the ship-and tower-building. Low-cost welding processes with high seam qualities are a special key for the strong growing energy sector in order to open up new markets. Laser beam sources of the newest generation enable faster production steps.

In the framework of the SFB 675 laser welding seams are inserted in steel sheets, which are typically applied in the automobile manufacture. The strain hardening of the welding seam as a frequent side effect is used to insert a locally hardened structure into the sheet, in order to achieve higher stiffness and strength of the component. Thus, locally strengthened sheets can be applied, which allow for a reduced wall thickness. Accordingly, the body weight is reduced, the fuel consumption declines and the range of electric vehicles increases.

A ZIM project with a SMU from Lower-Saxony intends to apply energy-efficient diode-lasers with a high effectiveness for the joining of mixed compounds from copper and aluminum. These lasers are needed for the production of solar absorbers. Due to the use of a processing head, which allows for the use of a single laser beam source, the energy consumption can be kept low during the production of the units. Thus, the environmental aspect of the product can already be found in the production process. Beside the mechanical characteristics of the joint, the thermal behavior during the lifespan of the absorber is also in the focus. This can be optimized by a specific adjustment of the seam shape.