Product Code: PIC2008_605

Characteristic Melt Pool Hydrodynamic Behaviors for CW Nd-YAG Deep Penetration Laser Welding
Authors:
Remy Fabbro, LALP (CNRS)/GIP GERAILP; Arcueil Cedex France
Sonia Slimani, ; Cedex France
Frederic Coste, ; Cedex France
Francis Briand, ; Cedex France
Presented at PICALO 2008

The hydrodynamics evolution of the melt pool during laser Yag welding of stainless steel has been experimentally studied by using a high-speed video camera that allowed us to analyze the main characteristic parts of such melt pools. Depending on operating conditions, very different and complex hydrodynamic behaviors can be observed when the welding speed varies from typically a few m/min to a few tens of m/min. At low welding speed, the keyhole is quite vertical embedded inside a large pool that fluctuates due to friction effects induced by the quite vertical ejected plume. At high welding speeds, laser interaction is only localized on the keyhole front whose inclination increases with the welding speed. Induced melt flow then dominates and generates the humping regime, with severe undercuts and periodic perturbations of weld seam. For intermediate welding speeds, the interaction of the vapor plume with the melt pool controls its stability. The conclusion of these experiments is that the dynamic pressure of the vapor plume, which is emitted with a variable intensity and direction perpendicularly from the inclined keyhole front, has a crucial role for the melt pool dynamics and stability in laser welding.