Parametric Study of Keyhole Behavior Based on an Approximate Theory

摘要

The present investigation addresses the mechanics of melt motion, vaporization and heat transfer and their consequence on operating behavior of the keyhole. The focus of the analysis is to determine the basic heat flux requirement for heating the material and sustaining the keyhole. This requirement is independent of the mechanism of energy coupling between the laser and the keyhole surface and is insensitive to whether the plasma plays important roles in keyhole formation. The study is based on a two-dimensional analysis for the mid-section of a deep keyhole, where three-dimensional effects are minimized. The results yield semi-quantitative estimates of penetration depths and vaporization rates as functions of welding parameters. While the majority of keyhole welding in industry at present involve relatively shallow keyholes, it is believed that the simplicity afforded by the two-dimensionality will lead to valuable insights which would benefit the study of these more complex keyholes as well. A discussion of the roles of laser optics and other factors on keyhole behavior is also presented.