Influence of hydrogen, oxygen, nitrogen, and water vapor on the formation of pores at welding of copper using laser light at 515 nm wavelength

Due to increased absorptivity of laser light at 515 nm wavelength in copper materials, welds with low formation of spatters and homogeneous weld depths can be performed.1 However, depending on the used process parameters, a process regime with strong formation of pores is observed. These pores are not resulting from instabilities of the capillary (process pores), but they are observed to result from the interaction of ambient gas with the melted material in the welding zone. Different gaseous elements such as nitrogen, hydrogen, oxygen, and water vapor, therefore, were applied to the welding process to investigate their influence on the resulting weld seam porosity. For this purpose, all welds were performed in a welding chamber. It is found that the reaction of ambient nitrogen with ambient oxygen during the welding process has a strong influence on the resulting weld seam porosity. Furthermore, pores are observed in the weld seam when the raw copper material contains an increased amount of oxygen. Depending on which copper material is used, strategies are derived to perform welds with low or no formation of pores.