Regensburg 2007 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 42: Materials design II

MM 42.3: Talk

Friday, March 30, 2007, 13:00–13:15, H16

Thermoelectric currents in weld pools — •Adrian Lange and Eckhard Beyer — Fraunhofer Institut für Werkstoff- und Strahltechnologie, Winterbergstraße 28, D-01277 Dresden

In order to achieve higher welding speeds and a better quality of the weld seam, external static magnetic fields are tested for laser beam welding. Experiments with fine grained steels and aluminium alloys show a reduction of the so called humping effect, an improvement of the top seam quality, and an influence on the cross section of the seam [1,2]. These phenomena depend on the orientation of the magnetic field. To explain that dependence, the existence of thermoelectrical currents was proposed in [1,2]. The interaction of that proposed currents with the external field shall generate a Lorentz force distribution in the weld pool which may be the reason for the observed phenomena.

Based on the Onsager relation for the thermoelectrical current density and the appropriate boundary conditions for the laser beam welding, thermoelectrical currents can be determined analytically [3]. Results for iron and aluminium are presented in a approximative two-dimensional geometry. Since measurements for the values of the thermoelectrical (Seebeck) coefficient of both materials are spare, different hypothetical material sets are tested and discussed.[1] M. Kern, P. Berger, and H. Hügel, Schweißen & Schneiden 52, 140[1] (2000).[2] M. Kern, P. Berger, and H. Hügel, Welding Journal 79, 72s (2000).[3] J. Paulini, G. Simon, and I. Decker, J. Phys. D 23, 486 (1990).