Product Code: JLA_14_3_146

Authors:
J. Tu
School of Industrial Engineering, Purdue University, West Lafayette, Indiana 47907

I. Miyamoto
T. Inoue
Department of Manufacturing Science, Osaka University, Osaka, Japan

In very deep penetration, the plasma inside the keyhole exhibits complicated behavior and the plasma plume covering outside the keyhole can also affect the observation of keyhole plasma. Measuring the light emission from keyhole plasma is an effective method to monitor laser welding processes in thin sheets; however, in welding thick sheets, several critical phenomena must be observed. In this article, we provide experimental investigations using a 20 kW CO₂ laser to characterize the wavelength contents of the keyhole plasma light emission. We also demonstrate that the plasma plume outside the keyhole can scatter the light emission from the keyhole plasma significantly. A scattering model is proposed and verified experimentally. The particles responsible for scattering are also identified. © 2002 Laser Institute of America.