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Due to their very good electrical and thermal conductivity copper materials are more and more demanded for industrial applications. For the assembly of copper based parts an effective and reliable welding process is required. At lower feed rates and high penetration depth respectively, welds in copper suffer from many weld defects such as pores and melt ejections. Keyhole instabilities during welding result in most cases in weld defects. In this paper high-speed X-ray imaging of the welding process is used to analyze keyhole instabilities with respect to the formation of weld defects. By means of X-ray observation of the welding process it is shown that bubble formation at the tip of the capillary is one mechanism which causes weld defects such as melt ejections and pores. Furthermore the influence of laser power modulation on bubble formation is discussed.
Heider et al. (Tue,) studied this question.