Contents
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9 Dynamical Behaviors of Keyhole and Weld Pool in Vacuum
Laser Welding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253
9.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253
9.2 Transient Coupling Model of Keyhole and Weld Pool
in Vacuum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254
9.2.1 Governing Equations in Vacuum Laser Welding . . . . . . . . . . 255
9.2.2 Boundary Conditions in Vacuum Laser Welding . . . . . . . . . . 256
9.3 Behaviors of Keyhole and Weld Pool in Vacuum Laser Welding . . . 257
9.3.1 Dynamical Keyhole Evolutions . . . . . . . . . . . . . . . . . . . . . . . . 257
9.3.2 Moving Weld Pool Flow Patterns . . . . . . . . . . . . . . . . . . . . . . . 261
9.4 Penetration Depth Increase in Laser Welding Under Vacuum
and Low Vacuum Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264
9.4.1 Mechanism for Penetration Depth Increase
with Ambient Pressure Decrease . . . . . . . . . . . . . . . . . . . . . . . 264
9.4.2 Finite Increase of Penetration Depth . . . . . . . . . . . . . . . . . . . . 269
9.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272
Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275