Process stabilizing potential of shielding gas mixtures in laser welding with CO2 lasers

M. Kern; M. Beck; Peter Berger; Helmut Huegel

doi:10.1117/12.270122

4 April 1997 Process stabilizing potential of shielding gas mixtures in laser welding with CO₂ lasers

M. Kern, M. Beck, Peter Berger, Helmut Huegel

Proceedings Volume 3092, XI International Symposium on Gas Flow and Chemical Lasers and High-Power Laser Conference; (1997) https://doi.org/10.1117/12.270122
Event: XI International Symposium on Gas Flow and Chemical Lasers and High Power Laser Conference, 1996, Edinburgh, United Kingdom

Abstract

A numerical beam propagation model has been developed to calculate the absorption and defocusing of a carbon-dioxide laser beam by the laser induced plasma plume during deep penetration welding. By directly solving the paraxial wave equation with a finite difference scheme, the model allows us to calculate the laser beam propagation through the plasma plume and to determine the 'effective' intensity distribution in the focal plane. In combination with a previously published model that takes into account Fresnel absorption at the keyhole walls and plasma absorption inside the keyhole, now a calculation of the welding depth as function of the process parameter becomes possible. In particular, the propagation model clarifies the role of plasma absorption above the workpiece. The calculations identify the defocusing of the laser beam by the plasma plume as the main mechanism that degrades the laser deep welding process. Absorption by the plasma is shown to be of little importance. Additionally, the propagation model elucidates the process stabilizing potential of shielding gas mixtures, especially of helium and argon mixed in a ratio of 3:1; a result also of phenomenological investigations that are used frequently in practice.

Citation Download Citation

M. Kern, M. Beck, Peter Berger, and Helmut Huegel "Process stabilizing potential of shielding gas mixtures in laser welding with CO₂ lasers", Proc. SPIE 3092, XI International Symposium on Gas Flow and Chemical Lasers and High-Power Laser Conference, (4 April 1997); https://doi.org/10.1117/12.270122

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