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Laser Keyhole Welding: The Vapour Phase

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The Theory of Laser Materials Processing

Part of the book series: Springer Series in Materials Science ((SSMATERIALS,volume 119))

Abstract

Several aspects of the properties of the keyhole and its relationship to the weld pool in laser keyhole welding are considered. The aspect of most immediate importance is the exchange of energy between the laser beam itself and the molten material of the weld pool. Many mechanisms are involved, but the two considered here are the process of direct absorption at the keyhole wall (Fresnel absorption) and the two-stage process of absorption of energy by inverse bremsstrahlung into the ionised vapour that forms in the case of the longer-wavelength lasers such as the CO2 laser, followed by thermal conduction to the wall. Consideration is given to the role of the Knudsen layer at the boundary. The possibility that the exchange may be influenced by the vapour flow in the keyhole is considered. More generally, the dynamics of the flow is investigated and the balances necessary to keep the keyhole open are investigated. A simple model of the interaction of the vapour with the molten material in the weld pool is proposed which can be used to investigate their interaction. Order of magnitude estimates suggest that it is far from simple but that some simplifying approximations are possible. The chapter ends with some basic models of electromagnetic effects in an ionised vapour as an introduction to the more comprehensive analysis provided in Chap. 7.

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Notes

  1. 1.

    https://www.en.wikipedia.org.wiki/Routh-Hurwitz_stability_criterion.

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Authors and Affiliations

  1. Department of Mathematical Sciences, University of Essex, Colchester, Essex, CO4 3SQ, UK

    John Dowden

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Correspondence to John Dowden .

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Editors and Affiliations

  1. Mathematical Sciences, University of Essex, Colchester, Essex, United Kingdom

    John Dowden

  2. Fraunhofer-Institut für Lasertechnik, RWTH Aachen, Aachen, Germany

    Wolfgang Schulz

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Dowden, J. (2017). Laser Keyhole Welding: The Vapour Phase. In: Dowden, J., Schulz, W. (eds) The Theory of Laser Materials Processing. Springer Series in Materials Science, vol 119. Springer, Cham. https://doi.org/10.1007/978-3-319-56711-2_5

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