Product Code: JLA_14_4_204

John Dowden
Department of Mathematics, University of Essex, Colchester, Essex CO4 3SQ, United Kingdom

There are several components to the motion of the liquid material in the weld pool in laser keyhole welding. Observations have shown not only that it moves in the plane perpendicular to the axis of the laser, but also that it moves parallel to the laser beam. It has been recognized for many years that the motion in the direction perpendicular to the surface of the work piece is important in connection with arc welding; it has, however, received less detailed study in connection with keyhole welding. The possible mechanisms are reviewed from a mathematical standpoint and Marangoni convection and viscous drag associated with vapor motion in the keyhole are identified as the two most probable causes of the vigorous motion observed in practice in the weld pool. The former is fairly well understood but the latter is not and it is this which is studied here. Simple mathematical models already available for motion in the two regions separately are linked in this article to demonstrate the ways in which the regions interact as a result of the vigorous axial motion in the keyhole. The significance of the role of viscosity is shown, and the sensitivity of the consequences of this linking to external conditions is demonstrated. © 2002 Laser Institute of America.

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