Effect of Process Parameters on Weld Penetration During Pulsed Nd:YAG Laser Welding

Weld penetration is an important parameter to be considered for given process parameters on a pulsed Nd:YAG laser welding machine. A gauge repeatability and reproducibility study (GR&R), components of variation study (COV), and design of experiments (DOE) are used to understand the relationship between the process parameters and weld penetration on 17-4PH H900, 304 Annealed, and 420 Hardened stainless steel pins joined to a 17-4PH H900 stainless steel block. These stainless steels are selected because of their common use for laser welding of medical devices. The function determined via the DOE is then confirmed empirically by trial laser welds at the determined process settings for different weld penetrations. For a given pulse duration (8 ms), laser beam focus diameter (0.4 mm) and cover gas flow rate (5 L/min), the linear regression equation describing the weld penetration, h(mm) as a function of Peak Pulse Power, Pp(W) is found to be h = 0.001657 (Pp) – 0.389 where 300W < Pp < 1100W.