Caption for
illustration 1: Laser welding of steel and aluminum. (Photo: LZH)
(September 3, 2015) For a definitive breakthrough of lightweight materials in
the automotive industry, new processes for manufacturing, testing and measuring
are necessary. For this, steel-aluminum hybrid welds are of great interest,
since they can be used for load-adapted, and at the same time lightweight
components. Within the project LaserLeichter (Laser Lighter), the Laser Zentrum
Hannover e.V. (LZH) is currently developing a laser welding process for joining
three-dimensional structures made of steel and aluminum in a hybrid design.
One of the challenges in welding steel with aluminum is to
avoid hard and brittle intermetallic phases in the welding seam. These phases
can occur easily, since iron and aluminum do not combine well. The goal of the
scientists at the LZH and their partners in the project LaserLeichter, is to
control the welding process as much as possible. Therefore, different measuring
methods will be assessed.
Establishing control
during and after the running process
For one, the engineers will be testing a spectroscopic
control of the welding depth, which measures the emissions of the plasma.
During the ongoing process, the composition of the plasma indicates the welding
depth, and allows to adapt the laser output accordingly. This control is
already being evaluated at the LZH for flat welds, and will now be expanded to
three-dimensional structures. Since the distance between the process zone and the
measurement sensors inevitably changes in the course of the process, detecting
the plasma emissions accurately is difficult. For optimal measurements, the
spectrometer will be integrated into an innovative, scanner-based processing
head.