Product Code: ICA10_502

Influencing the Melt Pool Dynamics with Short Pulses
Authors:
Rudolf Weber, Institut Strahlwerkzeuge IFSW, Universität Stuttgart; Stuttgart Germany
Roland Gauch, Institut Strahlwerkzeuge IFSW, Universität Stuttgart; Stuttgart Germany
Thomas Graf, Institut Strahlwerkzeuge IFSW, Universität Stuttgart; Stuttgart Germany
Presented at ICALEO 2010

The details of the melt flow dynamics in deep penetration welding as well as in laser cutting are still not completely understood. In addition, control of the melt flow might help to suppress or eliminate defects such as spattering, humping or dross formation.

The present paper describes the use of a short pulse laser to influence the behavior of the melt flow. First results show that the melt pool dynamics can be influenced very significantly with less than 1% of additional average power of pulsed laser radiation.
A 4000 W lamp pumped cw solid-state laser focused to a 450 µm spot was used as heating source to generate a keyhole and the melt pool. A diode-pumped Q-switch laser delivering 20 ns, 4 mJ pulses at 4 kHz was used to influence the melt pool. The two lasers were overlapped in the interaction region by angular multiplexing. The position of the QS-laser could be adjusted arbitrarily with respect to the cw laser. The experiments were made on sheets of stainless steel and aluminum and analyzed by means of a high speed camera.

Completely different effects were observed depending on the QS-laser position with respect to the keyhole and proved that the melt pool dynamics can significantly be influenced with the additional short laser pulses. These preliminary results allow estimates on the physical quantities such as short pulse absorption, energy transfer and melt flow speed.