Long Pulse Laser Micro Welding of Commercially Pure Titanium Thin Sheets

The paper deals with the application of a long pulse, lamp pumped Nd:YAG laser source in welding thin sheets of commercially pure titanium. An experimental campaign was designed and planned by means of the Response Surface Method (RSM) in order to assess the effect of the main process parameters on the weld bead penetration depth, width and general morphology. In particular the role of pulse duration, pulse peak power and pulse frequency was determined by means of optical observations and statistical analyses. Weld bead penetration depth, width and overall geometry were measured and related to the process parameters, in order to assess optimized operating process windows. The results point out, in particular, that pulse peak power is responsible for weld bead penetration depth. Pulse duration, on the other hand dominates weld bead width: by means of an in-depth analysis of these results it was pointed out that sound weld beads, characterized by the proper morphology, can only be achieved by means of a proper balance between these two parameters. A too high peak power, in fact, easily leads to the right penetration depth, but it tends to produce spatters, porosities and drop-through in the weld bead, while acting on the pulse duration the right morphology of the weld bead can be achieved.